Code:
tex_file ["Interface\\AddOns\\LitePanels\\media\\**tex_file**"]
Filename of your texture if you choose to use one. Width and height of the
image itself must be in powers of two (8,16,32,64,128,256,512)
If you put the files into the media folder inside the addon's folder, you can
set this to the filename only, otherwise you must give the whole path.
Did you make sure the texture has the right width/height?