Try this. It should blend in with your forums background.
Edit: I've just previewed the user images and it seems they already have been embedded with a white matte. The Attachment (below) will still show a white background. You'll need to make the modification and save directly from the PSD image.
Edit: Seeing as the images couldn't be saved out to compliment your colour background, I quickly designed 3 icons (they don't look great) but then, I designed them very quickly because of other obligations and I just couldn't spend alot of time on them. The preview is below if you want them, Just let me know, and I'll save them out individually for you.