You wanna make some backgrounds of your own, it's pretty easy.

mascot_inv.png will replace your inventory background.
mascot_chat.png will sit in the back of your chat background.

There should be enough examples here to get the size necessary for each image.

They handle transparency so you are going to want to adjust the opacity of the images you use. It looks like ass if you don't.
50% is a good number for chat backgrounds.
35% is a good number for inventory backgrounds.

To install navigate to your .vscape2/sprites directory, replace the file that's already there.
Don't worry, purple is just a placeholder, they don't need to be purple.

A good rule of thumb is to set them read only, as cache updates have a habit of overwriting them.
You need to completely restart your client after you install a background for it to show up.