In this guide we will add a custom image to the background of the cellphone accessory and learn a few tips on adjusting the brightness of the screen with the image.
Video Guide
Programs & Setup
Step 1:
We will need to have an image editor, an archive utility such as WinRAR or 7Zip, an image or logo for our decal and the Open Def for our mod.
I will use paint.net for our image editor because it is easy to use and free. Download here and install like any other app or program.
If your on a Windows machine, you can get away with not having to download anything to extract the Open Def, If you plan to repack a mod then I suggest using a 3rd party application. I will be using WinRAR. (link) If you plan to use an archiver regularly or more than a coupe times it is advised to install it rather than use a portable version, with an install you have more control and ease of use with right click menus and the ability to set defaults for one click operations.
Because you are here I assume you have an idea or image for your decal already so we will start with the process of unpacking the Open Def, you can skip the next step and edit a file directly in the archive itself but it is not recommended for many reasons.
Step 2:
If you have unpacked/extracted the open def already you can skip this step and go to the editing section below.
We will be extracting the open def (iw900_opendef_vx.x.scs). Rather than unpack it to a folder somewhere to work on then repack it as a mod, we are going to unpack it directly in your ATS mod folder.
By doing this we can save time and eliminate the need to pack the mod up every time we make a change. We can just edit the file and reload a game save to check our work. Just be sure to activate the correct mod in the mod manager….meaning this new folder your making and not the original packed mod. I will refer to this folder I am creating as the IW900 OpenDef folder from now on.

Create a new folder inside your American Truck Simulator/mod folder, you can name this anything you like just know that the manifest is responsible for the display name in the mod manager, meaning if you named the folder ‘my_cool_mod’, it will still show in mod manager as IW900 Open Definition.

Open the ‘iw900_opendef_vx.x.scs’ with your archiver of choice and extract or copy all the contents to your new folder you created.

The two main folders we will be focusing on is the ‘decals’ folder and the ‘UV MAPS’ folder. UV maps are just the templates for skinning, and the decals folder is where you will save your finished image.
Go to editing section
Editing Image
Note: You cannot resize the image for the cellphones or it may be cut-off or positioned improperly.

Open the ‘decals’ folder and select the background for the cellphone you want to edit and open it in your image editor.

If you would like to use a template to locate your image you can open the proper template from the ‘UV MAPS’ folder in the open def.

This is the blank background for the cellphone. I have selected the “Eyephone” here but i will save it to both backgrounds for now.

This is the template for the “Eyephone”. I will not be using this but you might want to position things with a reference. If you want to learn to use the template check out the decals guide here.

If you haven’t already, open the image you would like as your background. I grabbed one from google for this. This image is 2160x3840px and our background needs to be 512×1024 so we will need to resize it.

Resize the image with ctrl+r or Image>Resize from the toolbar in paint.net, make sure maintain aspect ratio is selected and select the width parameter and type 512 and click ‘OK’. You may need to play with your image to get it to fit right or crop it and position. This will get you close to the size you need. If image is to short undo and resize the height to 1024 and try that.

You can see that by resizing with the width my image is 910px tall, we need it 1024px tall. So we can fill in the space with black (not best option), or undo and resize the image from the height parameter and then just position image sacrificing some of the width. I will be doing the second option.

Now this image is resized from the height parameter, making it large enough to cover our entire 512×1024 cellphone background without distortion or filler background.
If you decide to use a filler on an image to cover bare spots it may have undesired results because of the illumination of the screen. See dimming section below for more info.

I will now copy and paste our resized image onto the black cellphone background we opened earlier.
If it asks you to expand canvas or keep canvas size…. select the “KEEP CANVAS” option.

Drag and position the image as you please. You can see the outline of the original pasted image and what is cropped out from the background size. This is good, we have a seamless image and will have 0 artifacts because the whole background has been covered.

Now we can simply click the disk (save icon) or go file save if you followed the steps correctly. If your like me and have to be sure…. use save as, set save type as dds (DirectDraw), and overwrite the original background with the settings shown below.

BC3 (Linear DXT5)
Generate Mip Maps
Super Sampling
Click OK
Testing
We can now start the game up and enter the mod manager.
You can skip this step if you have edited and activated the open def already.

Replace the original Open Def mod with the one you just edited. You can check the package name in the mod info to make sure you have the right one activated. Open Def goes above the truck base.

Go to the shop and locate the accessory node you want to add phone to, Dash Mount or Windshield Corner and select your preferred cellphone (non-gps).
Next I will show you one way to dim your image if it is too bright.
Dimming Screen
In this section we will be taking an image that is too bright in game and dimming it to look better at night.

Here is an image that is a little too bright at night time. Its not bad but could be a little dimmer.

On our image we will add another layer, called Layer 2 in my example. We are going to click the wrench icon outlined in red here, while our second layer is selected.

Select a light shade of grey (gray) and bucket fill your whole image. I have only done half an image here to show the results.

Once your image is filled in go to the top menu bar and select Image. We want to Flatten the image (ctrl+shift+f) and save the image to the proper location described previously.
We can now reload our gamesave or profile to check changes.

With a quick test you can see how much that affected the brightness of the background, all you need to do is find the balance your looking for with a little trail and error.
Again this image has only been dimmed on the top half so we can see the difference.
Notes:
Filling an area that is blank to make up an image could leave undesired results, artifacts or lines in your illuminated image even if you do not see them on the raw image itself. Scaling or stretching your image to fill the complete area is a better option.
You can always fill the bare spots as long as you blend the edges to rid yourself of hard lines.
Trial and error are the best ways to learn…have fun.