The checkered background isn't really a part of the image, its just something to tell you that its blank. For example, save the file and view it with another (non-editing) program. The checkerboard pattern won't be there.
A Forumer forum can't have anything edited except for basic things. You can't add special things because you're not fully in control of the forum. The servers belong to Forumer Therefore, to sum it up, no.