The website Brands of the World hosts a large collection of logos of various brands from, as you may have guess, around the world. Not just any type of logos, though, but vector files of them. Which means that they can be scaled up or down with no loss of resolution. These are the types of files designers generally prefer to use because they tend to be much more flexible that flat rasterized images. (Like those you see on just about every web page.) A quick search on the site, too, yields several pages of "comic" related logos including some character drawings along with the logos.
Careful notice will show that not every piece of art is really useable. Here's one of two logos uploaded for Comic Con International...
So I have to wonder how no one has tried cracking down on the site before. It's useful, certainly, but I would think somebody would've gotten their knickers in a twist over it.
But in any event, it's a neat resource that I have actually used from time to time. (Generally, when clients are being stubborn/uncooperative even though they're paying me to do their work.)