Are the images important in their own right? That is, do they come up often in image search? I assume you are not concerned about hotlinkers ;)
Remember that image redirects, unlike page redirects, are only for search engines. People don't bookmark images. (Well, sometimes they do, but you probably didn't want them to.) So the images themselves are only worth redirecting if Image Search-- in, ahem, its new* improved form
--is an important part of your traffic.
Personally I wouldn't bother. The search engine will ask for the old images and pick up a 404. But at the same time they will be crawling the redirected pages which contain references to the new images.
from http://www.example.be to http://example.be
That's not really a redirect. On one hand the search engines will consider it Duplicate Content if you enable both forms-- but on the other hand they know perfectly well that it's all the same site. If the images on your pages are correctly linked, the domain part of their URL will automatically change when the page URL changes.
This last part is an academic question, because you (or your clients) already have a catch-all redirect that intercepts all requests for wrong-form-of-domain-name and redirects to correct-form-of-domain-name. If you don't, you should. Go add one right now.
* I detoured to check. google dot be does the new-style image search. At least if you are coming in from a US IP.