Here are some bookmarklets (or favlets, or whatever you call them) to pop up a
new window with the specified new large cover art. Of course, mileage may vary
as the new eM system solidifies.

To use: add these to your Bookmarks or Favorites (depending on your browser).
When you're on an eMusic album page, click the bookmark to launch a new window
with that size art in it. Pretty simple, huh?

eMusic Cover (60px) (why?)

eMusic Cover (155px)

eMusic Cover (300px)

eMusic Cover (600px)

eMusic Cover (1400px)

The Code (for the curious):
javascript:var d=1400;$('img[src*=es/al]')[0].src.replace(/\/um\/\d+/,'/um/0').replace(/\d+x\d+/,d+'x'+d));void(0);

The more observant among you will see that you can change the "d=____" bit
to change the size of the image.