This was just a thought that came to me this evening. Deviantart (www.deviantart.com) is a huge art gallery on the 'net. It has built in compatibility with PicLens and is very easy to browse and navigate. Wouldn't it be a good showcase for the skills of the Guild?
A possible set up would work like this:
One account under the name of the guild.
Maps would get uploaded there once they had been posted in the Finished Maps section, and possibly only after they had been vetted by the CLs for quality, or if they had got a certain rating from the Cartographer's Guild members (I believe we can rate posts, but that we generally don't ?).
A deviantart gallery can have subfolders. This would allow the folders to be organised in the same way as the forums here are organised - regional, world, dungeon etc.
This would allow for an easy way to scan through the collected maps of the Guild, without having to do hefty searches through the forums. It would also expose the guild to a lot of wider publicity.
Two things to make clear at this point. Firstly, deviantart has a clear implementation of the Creative Commons licenses so it is very easy to make sure art isn't lifted for dark purposes. Secondly, when you upload a piece you have a comments section. I would suggest that the name of the person who created the art would be clearly specified here to make it obvious who to contact if someone wanted to use the art under the CC licence.
Just a thought.