Some random thoughts.
You didn't mention if these are print or pdf.
If pdf, consider offering a hex grid background to broaden the appeal and usefulness. My group often uses hexes for outdoor stuff even in D&D type games because it simplifies movement and combat. Squares are still easier in constructed dungeon environments even in game systems that specify hex grids like Gurps.
Check with a local Kinkos type place and find out what size(s) they can print and approximate cost. Offer pdf maps in those sizes. Even if you offer the maps in 8x11 sizes as well. Printing several 8x11 pieces and piecing them together can be a PITA. Plus it might wind up being cheaper for the end purchaser to pay Kinkos to print them out on large paper then buying the needed toner refills to print them at home.
Offer toner friendly versions as well. In your examples, make the brown areas very lightly shaded vs the current full coverage.
If you have access to a dungeon tile set like Dwarven Forge or equivalent, consider making some smaller maps that can be replicated with tile sets. Maybe build the physical dungeon first then draw your map to match.