I like patterns that tell you what size the units should be when put together also...every step of the way. Lots of pictures is good, and I like the suggestion of giving quilters alternate ways of creating things like HSTs, but then you would have to alter the cutting directions for each way and that would be confusing. I love Judy Martin quilts but I hate the way her directions are given - too confusing and frustrating, flipping to the back of the book to find a template, just give me the size of the square, triangle, rectangle in the directions.
When you have your testers make the quilts, ask them to do different color ways that could be used in the photos. You could also ask them to quilt them in different ways - E2E free motion, panto, custom - so buyers of your patterns could see the different possibilities. I know so many quilters who choose to make a quilt in the exact same colors/materials as the pictures on a pattern.
If you are using a new method of creating a pattern (like strip-sewn stars) that need detailed drawings/photos, don't skimp on them because the cost more money to produce, but they are essential to the success of your buyers...they fail with the first quilt designed by you, they won't be buying more.
I hate having typos and errors in a pattern - a good editor is important. It there are typos, I figure the person was in too big a hurry to get the pattern out to care about quality...and I wonder what else was rushed and wrong!