It is illegal to swap and share roms. It's arguably legal to use roms on a different device if you own them and have an appropriate licence.

The images you refer to are showing the latter, and not advocating anything illegal. They are showing single images from those roms which is legal under the 'fair use' laws, which allow a certain percentage to be published (is it 5%?)

If maemo.org were seen to be promoting, encouraging or even allowing the sharing of roms, the relevent companies would initiate lawsuits to shut the place down. It's not worth it, given that there are plenty of other places on the net you can have those discussions (they keep moving to avoid prosecution).