Since the advanced search feature can sometimes take a while, is there a way to display a please wait message until the results appear.
Also is there something going on with spammers and the tags on the forums? All I've put in the tag field is the term "advanced search", but I imagine there will soon be tags for other things.
Yes, there is something going on with spammers and (most visibly) the tags.
The forums are inundated with spam messages lately, and while the forum software is doing a relatively admirable job in filtering the bad messages out, the tags seem to remain.
As to your real question, the first thing I'd try is running OPTIMIZE TABLE on all your Omeka tables, but particularly the element_texts table. This can often make a world of difference in the advanced search's speed.
You should be able to rig something up with Javascript if you do want some loading message anyway, but something seamless might be tricky, since we generally don't send any output until the next page is done loading.