I see a potential shortcoming with this system as is, which used to be present with the Hot 20 until I pointed it out and it was resolved. How much of a problem it will be will depend on how many people view the galleries via the Art Charts in comparison to how many people view the galleries via other routes. Here's what might happen:

Member checks out galleries via Art Charts.
Sees a likeable image and adds it (and/or artist) to favourites.
Image (and/or artist) gets another "vote".
Member leaves galleries.

If a large proportion of members view via the Art Charts then the result is that the Art Charts become feedback loops. Popular images in the list get "votes" because they are visible in the list, therefore they stay in the list longer - ready to receive more "votes"...

The funniest example of feedback loop is the "Most Viewed" gallery. The most viewed image ever on Renderosity, by more than 10,000 views, is a fairly mundane "big-boob" example from 1999! It's the most viewed and always will be because, essentially, it's the most viewed.

When I pointed out this feedback aspect of the Hot 20, the system was revised slightly so that the ability to vote for an image wasn't present when an image was viewed via the Hot20. The viewer could still vote, of course, but they had to jump through the (fairly easy) hoop of going to the artist's gallery and voting from there. That gave a buffer to casual voting from the Hot 20 route.

Again, how much of a problem this might be will depend on the popularity of the Art Charts. If most people view the galleries via the regular routes (new, software, genre, etc) then the Art Charts might* be more genuinely representative.

Having said all that, I should point out that this is an entirely academic observation on my part. Personally I am not bothered at all whether the Art Charts are representative, nor whether they are "abused".

*And based on the observation from the Art Charts that hardly anyone is currently bothering to add images to their favourites, my bet is that once the little voting clubs that bothered so many in the Hot 20 cotton on, they will have an absolute field day. Will Fractal Seashell get to Number One? Bravissimo, my mind is blown! ;-)