Hi,
You just want to add an image to a button?
I'm not sure how to do that in the designer - I do all my stuff programatically.
In the code you can add a line like the following:
btnPvP.SetBackgroundImage(LoadBitmap(File.DirAssets, "PvP2.png"))
Obviously you would replace my button name and image file name with your own, and you have to add the image to the project via the Files tab at the bottom-right of the IDE.
Someone must know how to do this in the designer, so hopefully you will get more answers.