In the original banner photo, I liked how they "sized" the actors to fit their prominence in the show (even if that prominence was soon changed via writing). Blake was at the center and largest, with Fallon and OG Cristal on either side of him appearing to be slightly smaller. Then they placed Steven and (I think) Jeff on either side slightly smaller than the two ladies, with Sam, Anders, and Michael inserted between these in what appeared to be the smallest images.
It's always easier to find a great single cast photo to use as a banner, obviously--even a 'shopped one like the photo I described above. It would be great if the show would release a 'cast photo' every season or so that would make the admins' jobs easier, but even the picture with the 'top four' currently being used had to be altered because it is taller than it is wide. If the CW would publish head shots of the cast with similar backgrounds/lighting, etc. they could be strung together as a banner would be perfect. I guess the $$$ were better used for Bo's caviar budget.