I only have two tiers; $1- gets pages ahead of time and $3- same as the first tier, but also NSFW monthly pinup, uncensored pages and bonus pages/comics Currently, all my patrons are at the $3 level. This is all I can handle between work and doing my normal comic page load.
I think if you're going to offer patreon incentives, make sure whatever you plan to do you have the time to do. You don't want to stress yourself out making your comic as well as trying to get Patreon rewards up. The kind of rewards you offer will depend on your comic, but stickers and custom art sound totally fine. Some people just want to offer support to their favourite artists and aren't really interested in the rewards, too.