It's possible to have a Start Location in-game, but player's start locations are removed at the beginning automatically, so I imagine that they do not, seeing as how they do not exist during the game.
I would be very surprised if unit-sprites do not count against the unit limit. I'll go test this now.
Also, some units do contain more than one sprite. Most notably, those with turrets (goliath, siege tank, science vessel, etc).
EDIT: Unit-sprites DO count against the unit limit of 1700.
I didn't mean the unit sprites, I ment the Start Locations that you are requied to place on the map, they dissapear when the game starts.
The thing about the unit-sprites was correcting battlekruser, he said that they don't count. You're right about start locations.
Edit: I guess I totally misread battlekruser's post. Nothing to see here, just move along...