Thank you for the quick reply.
My current problem is that if I add a subdomain on cPanel it’ll let wpmu handle the request. This is what I want because wordpress does all the /files/… to wp-content/blogs/… translation but wpmu won’t find the blog with the images prefix. I could just change the upload dir in settings but I want multiple images subdomains so that won’t work either.
Do you have any idea how I can solve this problem?
After this is solved I think that all I have to do is rewrite the urls in .htaccess and add a filter to translate existing images’ url to the new subdomains.