I keep trying to add banners to my communities, but get errors about size limits etc. help appreciated.

Any and all resources welcome on mod101 The questions that brought me here are: 1. How do I mod someone else? 2. Can I create tags so users can sort based on topic? 3. Assuming 2=no, what's the max on sticky post counts? I have a metric fuckton of info I want to post on a new community I made, and I don't want users to get lost.