I am planning since quite some time to make some tilesets, but I haven't settled yet on a style.
the last months I have been significantly improving the 8-Bit Series and started a 16x16 Icon series and also there is a new Monster/NPC assetpack upcoming too.
There are tilesets available on itch.io, but I don't know which one would suit your needs best and/or then fit best together with some of my assetpacks.
What I can say is that I'd also love to offer some tilesets fitting together with my RPG series, but that also needs just more dev time from me.