Bottom line is the Bottom line, they said so themselves. They want that puppy to scream "BUY ME, BUY ME" and jump off the shelf. I believe electroglyph mentioned they should handle this in the same manner the Pros do & approach artists. I agree, along with adding the typical Sub-content on the cover as well. You pick up any magazine, the image grabs your eye, & all the text/paste-up gives you enough info to wether you want to open it.
Whatever happens, Renderosity has grown from grass roots and will continue to grow along with your typical "growing pains".
As far as Genre, well this site started based on Poser, it's the main staple here and will probably dominate for some time to come. Yes, it's only logical that they'll be fair and spread the interest across the board, but it is their site & Mag.
Eventually contests will most likely become "in-house" events, just as the pros do.
"Live in the Moment & Render like mad"
ICM

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Ockham's razor- It's that simple