I'd change 1 thing from this tutorial: Use the pattern you just made against the shade to check for size, NOT fabric. Once you cut it, it's too late if wrong size. You can adjust by trimming fabric where needed once it's been cut.
DIY: Mod podge a map to a lampshade.I really like the many suggestions for recycling old maps and atlases. You could even concentrate your shade on specific locations that someone likes to personalize the shade for them.
Custom Lampshades: How to design an exclusive lampshade