I’ve been using Campaign Cartographer 3+ for a few years now. It does support image backgrounds (and depending on your image it might even trace it for you)… … but I should say that it does have a somewhat steep learning curve. It’s more a CAD tool than a drawing tool.
You will most likely need to read the tutorials and maybe watch a few videos to be comfortable with it. Luckily, there’s lots of videos and a forum with tons of friendly people.
It’s not cheap but it just so happens that there’s a Humble Bundle ongoing for the next 5 days:
https://www.humblebundle.com/software/maps-extravaganza-revisited-software
You’d have to go for the highest tier to get the base program.
Mac? Linux?
It runs decently under wine on Linux, but I've heard Mac users struggle.
But yeah, I get it.