FYI Ace, I love the animated header. I like it better than the normal header, because you are not limited by how many images you can put into it! (not least because it's totally pimping my images
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As an idea, can you make it so when you roll over an image it has a click-able link to the art. I believe later iterations of flash will give you AS much control over this as a normal hyper link (I.e. open in new tab, which is what most of us do, hence not wanting that silly popup image window thingy you disabled!) just so people can go and visit the pages these images belong too (be that the WIP area or galery etc). It's something several people have noted to me, that they see some images in the upper header, but you can't click on them (and that was of the old version specifically, in this case).
I am not trying to have a go at the work that's been done or anything, so far it is a lot nicer than the old style which I think was too busy, and as you said, inflexible. But several people have noted too me that SFM is quite a busy design, which is very distracting on the eye. Partly this is because forums in general have a HUGE information overload issue, but thinking of how the design of the site can help with that could help to make SFM an inspiring forum. To be honest a lot of forums need to make themselves 'look' interesting, because there's little else other than some text in here: SFM is incredibly image rich, so, in a way it almost needs to have less ego, it doesn't really have anything to prove!