
Not too sure what size you want? here are some guidelines to get you started!
first, let's decide if you want pan wells or an open concept.

open concept
pan
wells

Things to consider with palette size & capacity:
pans to be stored
Shadow pans come in a multitude of sizes ranging from 15MM to 57MM most commonly. Are your pans circular, rectangular, square, odd shaped? Storing multiple sizes together? Sorting by color family or makeup brand?
proportions
All customs are digitally designed prior to production and must be taken into account when designing artwork for the cover. I.E. a square perimeter on artwork won't look the same when translated onto a rectangular or circular shaped palette. If you're thinking about having labeled pan wells, is there room available between them?
storage constraints
Think about how you currently store makeup palettes. My designs are handmade and are anywhere from 1-2" thick whereas most manufactured palettes are less than 3/4". Do you store your palettes flat or vertically? Shelf display or drawers? Have curious kiddos exploring and need to keep your collection secured?
content impacts
Are you a content creator and have to work with photographical restraints like light reflection, physical space, content type? Consider those variables when discussing design.
palette aesthetic
If you've looked at my base designs, some are shaped irregularly and some are the basic 4 sided polygons. Flat sides can be added to enhance storage options or you can keep the design more traditional.
budget
Want to get the most storage for your budget or are you more interested in the physical design and artwork? Let me know about budget constraints prior to design so it can be taken into account. Design and capacity fall on sliding scales - minimal design + large storage could be the same budget equivalent of a more complex design and lower storage capacity.