well that's something you can play with...I mean train.

Round 1. Loose combos.
2. Fast and sharp.
3. Full extension. (for me this follows 2 because often when I've seen people shadow box throwing fast combos they shorten their punches. This brings your technique back)
4. Focus on power.

etc. You can make it so it's just punching, add in footwork e.g move after ever shot or comb, add in head movement. Working these from the centre of the ring or outside or on the ropes.

Lots of things you can focus on. I'm too lazy to write more but you get the idea.