I can't see any pictures in the RSS feed anymore. This happened just after the server upgrade.
I've talked to several other people who have experienced the same problem.

I'm having similar problems, I can only view thumbnails of posts over a year old, and only a few of them at that!

E621 has an RSS feed?

It does O_o

Lol its like that guy who discovered the forum XD

It does have atom feed

http://e621.net/post/atom

Hmm... It's an Atom feed, actually - not that it makes any read difference - and <clickety> ...it works fine for me.

Can anyone else get thumbnails in Google Reader? And explain to me how.

it seems to be that the thumbnails are just arriving later than the post itself. things posted hours ago now have thumbnails both on the site's feed and the atom (rss) feed. but posts more recent have broken thumbnails.. just an observation. I've got no solution. I've even temporarily unsubscribed from the feed, I just don't have the time to click every single one.

I think it is some sort of anti-hotlinking script or something. If I take one of the missing image URLs from the feed and paste it directly into my browser, it redirects me to a page that appeared to search "md5:preview/4e/e5/4ee53653d08f56bbf2b152ef511a7cb3".

If I fix the search by removing the "preview/4e/e5/" and find the image in the site, the thumbnail, same URL as the one in the feed, now loads fine.

Based on all this, I'm betting that for the thumbnails to load your Atom aggregator needs to provide referrer information that originated from one of e621's domains. Unfortunately, my aggregator has no such feature.

Somebody should fix this, as it makes the Atom feed useless.