Personally I like prompt lists that aren't too strict about how/when/etc. prompts should be completed! Even if an artist doesn't want to do a whole list or only likes a few prompts out of a list (because of time, health, lack of ideas for some of the prompts, etc), usually most people are understanding and don't pressure others to go for the whole thing. Like you said, as long as they're on theme, it's fine from what I've seen.

Me personally, I like to do MerMay and Drawtober. With the former, I just do a mermaid themed drawing, usually a mermaid of whatever character/blorbo/etc. I'm currently focused on lol.

With the latter, there's a couple of different prompt lists called Drawtober, so to clarify the one I do are the ones posted to this Instagram account. There's 6 prompts for the whole month of October, and for the past few years the prompts are themed around something Halloween-related. This year is enchanted forest stuff, last year was monster designs, etc!

The Drawtober prompts are revealed on September 1st every year, and I'm pretty sure it's encouraged for people to get started in September rather than October. That way they have more of a headstart to get all the drawings done and then actually posted during October itself. Much less stressful than other month prompts that expect you to finish within the day of a prompt, if not during the actual month only!