Haha, will that ever change?? You know I constantly wonder how, with current prices and all that, some people are still hanging around on 1024 rez. Ho hum, there's going to be skins based on such in about 6 months time from what I gather. People will be able to choose how they want the site to look...
In all cases, it's down to basic usability, though. I see (and end up repairing and redesigning) a LOT of sites created by graphic designers on 23"+ monitors who've never thought to check what their work looks like with a smaller fold/view area.
With 2000 AD, I suspect more of the target market than usual with have large monitors; however, laptops are increasingly common for a home PC, rather than a desktop, and the popular sizes for screens are from 13"–15", which largely have about 500–650px vertical view area using defaults. Even with larger monitors, it's not a great idea to take space for granted anyway—most users I've seen with 20"+ monitors don't surf full-screen.
As for standards support, I see you've shifted everything over to CSS (something that I tried to push during my last meeting with you guys a few years ago, but that didn't happen for all sorts of reasons), and that means you should be able to get the site working across Opera, Safari and Firefox with zero problems (bar, perhaps, minor font-size issues across Win/Mac, due to antialiasing differences). IE 8 should be largely a happy bunny, which means conditional comment over-rides for 7 and 6. That said, if your code's clean, such over-rides should be very minor, bar, perhaps, issues with hasLayout, which is the thing that causes most of my IE layout problems these days. (That said, hasLayout can usually be dealt with by either specifying a height of 1% via a CC or a zoom level of 1.)
And, uh, I'll turn off the web-head now.
As for the covers, I have no idea as of yet.
I think that's a really good idea. A lot of major mags do that, including IFX, CA, etc., and it could add real value to be able to see the cover art devoid of other junk. Not that 2000 AD tends to have that many coverlines, but it's still a good idea.