I am a huge roleplaying nerd. Table top RPGs are one of my favorite activities and while I'm normally a player, I do like to create assets for games my husband runs, or just for fun. Maybe I'll run my own games sometime, but for now, I'm content just being a backseat world creator.
I use Dungeondraft to make most of my maps and Clip Studio to edit/modify details/do touchups.
I use many different asset packs depending on the map I'm making. Some of the notable pack creators I use assets from in the following maps are:
Crosshead, Forgotten Adventures, GnomeFactory, Spiffeigh, Tyger
Most are fantasy assets, but some offer good modern and futuristic asset packs as well. I highly recommend supporting these asset creators however you can.