Did I overdesign my MySQL database (users/companies/products)?

Looks good, well normalised, to me at least.

I notice that each product can only belong to one company. If that's what you intended that's fine, otherwise you could have product have its own PID and have a product_company relation table, which would let more than one company sell a particular product. Depends who administers the products I guess.

I did notice that the user table is called 'users' (plural) and the others are singular ('company', 'product'). That's only a minor thing though.

No good.

Example: I want multiple pictures of my product. Please let me upload more than one picture of my product!