Before humans developed language, did we think in pictures?

Yep. We did.

the earliest languages came in the form of pictographs - later came hieroglyphics , then came abstract language. Chinese is probably the oldest of the language forms still in regular use.

I surmise it is so for if you look at the etymology of most words they are originated from describing how something looks.

I have heard some people think in pictures and others in words. However, I still think most people think in pictures for words express what we see mentally.

The farther I get into my anthropology class, the more I learn that these are the types of questions no one can answer, cause we weren't there so we don't know. I think so. I've often wondered if thats how my dog thinks...

humans always had language...so no.