You said you were going to switch to Tango icons. You might want to consider taking the images and doing PNG compression on these and/or compare to GIF vs. JPEG vs. PNG in some cases. This could lower your bandwidth utilization and make the pages snappier.
Also, when I post a new topic, it shows all these fancy icons and so on. If you minimize that a little, you might lower your bandwidth requirements too. Links or buttons with things like "B", "I" on them would do just fine for me. When I need an emoticon, and I rarely do, I could click on "Emoticons..." to choose one.
Another option is to take the banner and make it a tiny bit smaller in height.
I don't mind the fancy gradient bar on the home page -- it sure draws my attention. However, I don't see a need for it much anywhere else. If it's not impacting your bandwidth, then I guess it's no big deal. But if it is, then perhaps you could consider replacing it with just a regular color.
I think the Emoticons thing on the left during a post -- that could be eliminated and, instead, an Emoticons link near the formatting toolbar would be suitable.
Poll questions? Who uses these? Could this be done in a different way rather than confuse people when trying to post a message? When I first came to this forum, that threw me for a loop and I learned, "Oh, I can ignore that. Okay."