Our great sponsors
-
SurveyJS
Open-Source JSON Form Builder to Create Dynamic Forms Right in Your App. With SurveyJS form UI libraries, you can build and style forms in a fully-integrated drag & drop form builder, render them in your JS app, and store form submission data in any backend, inc. PHP, ASP.NET Core, and Node.js.
Adding to the other answers, there are also -besides Photoshop, Gimp, etc- specialized tools to draw fantasy maps. The site mentions Wonderdraft [0], but there are a bunch of others though not all of them support using external brushes.
Some other tools in this space may be Watabou's tools [1], Azgaar's tools [2], Inkarnate [3], Mapforge [4], or quite a few more which you can find links to in this list [5]. Again: you could use these brushes with some of these; not all support external brushes.
[0] https://www.wonderdraft.net/
[1] https://watabou.github.io/
[2] https://azgaar.github.io/Fantasy-Map-Generator/
[3] https://inkarnate.com/
[4] https://www.mapforge-software.com/
[5] https://www.mapforge-software.com/links-to-map-making-apps/