Hi Mike, welcome to the forum!
Have you checked out this guide to speaker placement from Dolby? It's a great resource to understand the general guidelines for where and how you place speakers for both 5.1 and 7.1 configurations.
Based on the image of your basement layout, I really don't think you'll benefit much from going with a 7.1 setup. The rear surround speakers in a 7.1 system should be several feet behind the listening position for optimal effect. Placing the speakers right above the listener (and pointing into the room) will probably be more of a distraction than an enhancement.
Also, keep in mind that ANY 7.1 receiver can be configured to operate as a 5.1 system. You can also set up the home theater as 5.1 and save the other two channels for a "Zone 2" for elsewhere in the basement (if your receiver has a second zone option).
The placement options for your side surround speakers would work OK for a 5.1 system, but if you do decide to go 5.1, you could probably put them almost in the corners, pointing out towards the middle of the room.
Ceiling mounting the surrounds is an excellent idea. They SHOULD be higher than ear level anyway.
Getting speaker placement roughly in the guidelines is a good start. If your receiver has an auto-setup utility (preferrably with a microphone) then that can be a really useful tool for correcting for less than ideal placement.
Best of luck. Enjoy the system.
