Derek,
I am not a sheath maker but from having them made and using them in the field this is a great first complicated sheath as you call it.
On the next one think of how a sheath will work on a trail in the bush, Your corners on the sheath may get caught on plants, vines etc. Also over time these corners will get bumped and frayed. Try making the next one to the contours of the blade and round your corners some. Its far better than I could do, I am just trying to help you get to that next level of your sheath making.