A few related questions.

Does anyone have a list of the enhancements between the original DagPic (for which there is source) and Andypic (without)?

Are there any other tools for adding/replacing images, especially one that can handle animations? I know there are other display-only tools.

Would there be significant demand if I have to start from the DagPic code and develop one myself?

I haven't seen anything detailing the differences other than the vague information in the readme files. What do you want to do that AndyPic can't do?

As stated in the opening post, add/change animations. I'd also like to be able to replace images with ones that have changed dimensions, create new files, and a few other improvements like that. Andypic can also leave a file unusable when it tries to do an update and fails, and I'd like to try and prevent that, as I'd need a lot fewer backups.

I'm not sure how much demand there is for modding vanilla Daggerfall these days. Most people seem more interested in just getting the graphics out for DaggerXL. I considered adding image replacement to Daggerfall Imaging 2, but ultimately decided it would be time invested in a feature most people wouldn't use.

It would be awesome to have such a tool, so don't let that stop you if you're keen on writing it! I love it when people develop for Daggerfall. Of course, you're also welcome to use any of my code/tools as a starting point if it helps. I release everything under the MIT license so you can do pretty much whatever you want with it. The Daggerfall Connect link in my signature will take you to the SVN.