ggg123

@CyDragonGMYT you need open iv to edit textures.

Download OpenIV if you dont have it. Then, on the right side of the address bar, click edit mode to enable it. Then go to Grand Theft Auto IV\pc\data\cdimages\scripttxds.img (browse in OpenIV, of course) and you fill find a series of files phone3d_hq_private, that end with a number and the .wtd extension. These are the textures of the in-game phones theme.

Double click on one of them (make sure you have edit mode on).

Now you can do two things :
-edit the textures
-create new textures

To edit them, first open the .wtd file. In the lower left corner of the window with the textures, click export all textures.
It will open a menu, saying "Please, select file format". In that menu, select the first option ("portable network graphics (*.png)").

Then, select a folder where to save all of the textures and edit them with software or on a website.
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If you want to use your own textures, click on "replace" in the top right corner of the texture file's window.
You can replace it with whatever picture you want.
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Also this seems important to me :

The texture named animated represents the animated objects over the wallpaper on your in-game phone's screen.

The texture named background is the phone's background.

The texture named logo appears over the background.
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I know this comment is about 3 years old, but I hope I helped!

@maxi_fisch that weapon is the pool cue. I've only seen it selectable in trainers, but its in the game.