Worktop freezers with backsplashes are an ideal choice because the backsplash will prevent food crumbs and debris from falling behind the unit. This will make cleaning easier, though all of the units are mounted on casters, so even if something falls behind, the piece of equipment can be easily rolled forward.
The compressor will be located on either left or right side or in the back. For back-mounted compressors, there will need to be a few inches of space left to allow for proper air flow. Some models are front breathing, though. This means there does not need to be any back clearance, because the intake and exhaust vents are on the front. Side-mounted compressors will need a few inches of clearance on whichever side the compressor is located. Basically, if there is any kind of air vent, give it some breathing room.