I agree with the above comment. In fact, from my experience on Steemit, it's best to upload a series of photos on one post. Begin with a good introductory paragraph, and include captions and explanations with each photo, and you'll most likely receive more "rewards" from the Steemit crowd.

Anyone can upload a photo or 2. But that's not the kind of content that the Steem boys and the whales are looking for. They prefer quality content, content that shows that you put a fair amount of effort into creating, and content that others will find both interesting and informative.

I'd say a general rule of thumb is about 15 photos per post, with at least a short paragraph for each. The content of the paragraph can be almost anything, as long as it is relevant, interesting, and decent quality.

Best of luck on Steemit. Full Steem Ahead.