If you have Photoshop you DO have a tool with which to create amazing maps.

Your world has a pleasant arrangement of landmasses, and other than being pixellated, looks fine. Really, if you have the RAM to deal with it, you can get crazy-good results with even Paint, just by starting with larrrrge canvases. I like what you've done thus far.

If you want something to print in a typical book, keeping the detail simple is a decent idea.

You have access to the premier free equivalents of the well-known expensive software packages - GIMP approximates Photoshop, and Inkscape approximates Illustrator. There's always a learning curve, but the results can be worth it. Example - I don't (yet) do vector styles in Inkscape, but I have found it excellent for creating curved labels.