For political content, be aware of the instance you are posting in. Lemmy.world is pretty good, but will often remove any posts about political violence, including guillotines and "Luigi" content. Lemmy.ml will remove content that is critical of communism, including Russia and CCP.

Politicalmemes could be a general place, but you're most likely better off posting your artwork in communities oriented specifically towards the political position your artwork is for.

I find that the best way of discover communities is to browse "all" and sort by 6 hour best. Do this a few times over a few days and you'll probably find communities that are suitable.

"Sharing artwork" or "offering your stickers for sale?" The former is fine, but the latter is likely to get you banned for spamming.

I'm happy to field your questions at !newtolemmy@lemmy.ca

For not specifically newbie questions but stuff you might feel silly asking on AskLemmy, you can go to !nostupidquestions@lemmy.world

For where to share your art: !artshare@lemmy.world

For where to share your political flyers: !politicalmemes@lemmy.world or !politicalmemes@lemmy.ca if they are anything like a meme. !usa@midwest.social is more loose in types of content allowed so your political art (if US related) might be able to be posted there.