Glad you like it! Yes, a complimentary battle background pack is exactly what I have planned next.
I hadn't thought about a boss monster pack but I like the idea, that would be a lot of fun to make.
That sounds wonderful, and I hope you manage to realize both of those packs. I'll buy them for sure. It's actually really hard to get your hands on (pixel art) battle background assets without hiring an artist directly (but that's quite pricey for a hobbyist).
Do you already have an idea of what environments/settings (and how many...ish?) you'd put in such a pack? While I assume it'd still be quite some time before you had it all finished, just knowing you where thinking about it made me really curious.
Good to hear there's a need for backgrounds. I haven't decided all settings yet but I'm currently working on a dungeon one (natural caverns) so that one is in for sure. Some that are very likely to make it in: Forest, swamp, desert, probably some castle or temple interior - I'll aim for 5-8 total I'd say.