There seem to be a glut of image sharing services geared for Twitter or the like, which of them should I stay away from if I care about the picture and which allow me to retain control over the photos?
The only reason that services which allow sharing option (TwitPic, imgur and even Dropbox) force you to share rights on your content is to allow the service to do its job, namely: publish this content.
Dropbox, for instance, had an incident when they changed the TOS: there was a big discussion, and Dropbox guys had to explain why they did that.
Here the citation from their explanation:
One of the main reasons we updated our terms of service was to make them easier to read and understand. It seems we’ve mostly accomplished that, which we’re thrilled about.
Some of you have written us with very understandable concerns about the legal-sounding parts. In particular, our new TOS talks about the licenses we need to run Dropbox. We want to be 100% clear that you own what you put in your Dropbox. We don’t own your stuff. And the license you give us is really limited. It only allows us to provide the service to you. Nothing else.
We think it’s really important that you understand the license. It’s about the permissions you give us to run the service, things like creating public links when you ask us to, allowing you to collaborate with colleagues in shared folders, generating web previews or thumbnails of your files, encrypting files, creating backups… the basic things that make Dropbox safe and easy to use. Services like Google Docs and others do the same thing when they get these permissions (see, for example, section 11.1 of Google’s TOS).
We wish we didn’t have to use legal terms at all, but copyright law is complicated and if we don’t get these permissions in writing, we might be putting ourselves in a tough spot down the road. Not to bore you with the details, but please take a look at the license term in the TOS. We think it’s fair and strikes the right balance: “This license is solely to enable us to technically administer, display, and operate the Services.”
So in the copyright world services have to protect from copyright owners to not being sued.
The short answer: if you want to share copyrighted work and retain full control, you should accomplish this with your own server, the only way you set the rules. If you decide to trust publishing to the third parties, you have to compromise.
Taking info from the link in @Sathya's comment above, the answer is to use Mobypicture.
Their page News: your content is yours is very clear (my emphasis)
Content Ownership: All rights of uploaded content by our users remain the property of our users and can in no means be sold or used by Mobypicture or affiliated third party partners without consent from the user.