First, prowl through the Discord mods UI forums
http://www.worldofmodcraft.com and look at the UIs. Many of them have download links, download the malls and yank out the textures you wish to use. Likely you will find the textures in the Discord Art folder, however it may hide in the other Discord folders.
You can also create your own. Just make sure you save your textures as an uncompress TGA with an Alpha channel. Also sizes need to be in a power of 2 (16, 32, 48, 64, 128, 256, 512, 1024) as in 32x16.