[Protoman]

I like the idea of this hack also, I can't write it but I can give some ideas atleast

Allow control of the number of images in sigs (right now you can only control images in posts/sigs -- 1 variable for both)
be able to set max image sizes
be able to mass remove/warn of oversized sigs (maintenance)
--warnings would remove the [img] tags and add a notice at the top, but leave the content for the moment.
decrease sig dimensions based on lines of text and font size
--take the font height for each line and subtract it from the overall total for the text and image
--defined by returns or characters/line limit variable maybe?
prevent [img] followed by text causing page to stretch horizontally, or insert a return and recalculate max sig size.
some sort of quote / code box controls
basically, anything that could force the sig area larger than the set limit.

again, just ideas.. but I would really appreciate this!
anything else I'm forgetting?