Can I make a recommendation?
If you are going to put ads on your site, use something you have full control over, works well with web comics, and you will feel good about displaying.
Don't use Adsense, which relies on a fair amount of text to display anything relevant and has been a poor performer for web comics. You will end up with all the trash ads that don't pay well on clicks, stuff nobody would want to click, for some of the sleaziest sites on the internet. That is pretty much how it performs on a web comic site.
Try out Project Wonderful.
Web comics were among the first to embrace that ad network, it doesn't rely on text. You will have full control over the ads that run, before they run, if you want it. The ads you are likely to see displayed are mostly for other web comics, blogs, and games. It's pay per day advertising rather than pay per click.
I think you'd enjoy it and even maybe look at it as a site feature, rather than the average run of the mill ads.