Allow multiple ajax-loader images per page

Currently it is only possible to display one element (mostly called "ajax-loader") that is shown during an ajax call.

There are use cases where it's desirable to have multiple elements per page and choose the "right" ajax-loader per ajax call.

For instance if I have a page with two subwindows, each of the pages showing content that can be separately reloaded from the server I'd like to see the ajax-loader images next to the "Load More" button I just clicked.