I like the case design, especially the way you have the sensor angled. I would think that you should be able to print that angle without supports.
Some ideas on the case design. Rather than having the tabs at the top and bottom for anchoring it to the wall, why not put your anchor points inside the case. With the tabs at the top and bottom, it looks like they could easily be broken off if the sensor is bumped. It looks like your case is two halves that snap together, so anchoring inside the case should be easy. Have a look at my case design that I did some time back, you'll see what I did for that. I used that same case design for a couple different sensors that I have done and it works well https://www.thingiverse.com/thing:2186286 This case design is the one linked on @sundberg84's openhardware page for the easy newbie board.