K1ra,

Image swap would be an entirely different mod and I assume you probably overwrote some necessary files when you installed image handler. The image swap javascript or jQuery may also conflict with image handler.

Diva, of worthy note and may have been posted before in this thread:

I installed image handler and ran into a problem with the image on the product page requiring the use of the _MED image which doesn't exist at all. I finally figured out that the ImageMagick version is only 3. So if anyone runs into this problem and checks this thread, perhaps this will be of some use to them.