Requested feature overview description.
I would like to suggest an enhancement to e621's RSS support: Increase the size of the thumbnails/images shown in the RSS feed. For some images the current size works ok, and you can make out what's going on, if you squint, but for most images your only option is to click on the image to see if it's something you want to actually view. Perhaps double the current size?

As an example comparison of thumbnail sizes here's an image comparing what Derpibooru's RSS thumbnail looks for an image compared to e621's RSS version of the same image. Derpi's thumbnail is 750 x 600 while e621's is 150 x 120 for an image that is 1280x1024 at full size.

Fair Warning: NSFW image at link (nothing too explicit though).
http://i68.tinypic.com/3469e2r.jpg

Why would it be useful?
It would allow RSS users to better see the content that they have a feed for.

What part(s) of the site page(s) are affected?
RSS feeds

Well, it's the standard thumbnails that get shown in the feed, and we don't really have any other sizes except the preview and full size.

It'd be nice to see the preview image in the feed contents but I don't remember how easy that would be to implement.