What size should my images be?

The system will usually show you the recommended pixel dimensions when you're uploading — follow these rather than guessing. As a general rule:

Keep file sizes small (roughly 300KB or under) — large files slow the page down without looking any sharper

Avoid images with text baked into them (e.g. a flyer-style graphic) — these tend to look messy, and you'll usually already have that information in your text fields anyway