To remove the embed code from your images at dA all you need to do is go into you profile, under the Deviation Management tab and deactivate your gallery. This doesn't prevent anyone from viewing your images, it just stops them from from being available to deviant Mobile.

As to letting people use images, I'm not so eager to look the other way as people disregard copyright. While you can't prevent people from using posted images as backgrounds on their computers, you can certainly require people to ask permission before using an image on a website or in any other fashion. Just because something is posted on the net doesn't mean it's free for the taking, regardless of whether or not they give credit to the artist.

It's all fun and games...
Until the flying monkeys attack!!!