Ability to exclude domains from imageproxy

[Numbered]

We want to see them in core. Typical situation: we want to use forever saving image to our server (if we choose 30d or 1d - it's not fix our problem). But users want to post their generated userbars in signatures.

For example:

 

This signature will update if new data receive. With imageproxy for that we can't see their update.

I very like imageproxy function and understand - it can't know about this type of images. But if you create setting for select excluded domains for imageproxy - it will be perfect!

Thanks