I've been spotting a number of quite cheap charms and 'embellishments' on sale that have been crying out to me. Quite a large number of these I've bought and squirrelled away for later use from The Works and a few other places.
Take this set for example, the mask could hang outside a theatre, buy four packs and you could build a clock tower using the clock one. The crown will work for either a pub or maybe a jewellers. I'll leave the others to your imagination.

There are several other sets I've got but have already been put into storage.
More thoughts to follow...
(*) Other celebrations can also generate exciting modelling materials too.