Most of the things I'd tell you to do can't be done because you are too far in the process, but here are some things to think about:
1. Exterior faucets. Walk around your place and everywhere you think "I'll never need a faucet here", put a faucet there.
2. Expansion joints on any pipe that goes under the slab. Would be a bit of a PITA to do it now, but still a better time than later.
3. Electrical - pay the electrician to number the circuit wires in each of the junction boxes, plugs, light fixture boxes, etc. Have them mark the circuit numbers in the fuse box, along with a good detailed description of what each circuit covers.
4. As-builts. Either do them yourself, or pay extra for them - but get good pictures of each wall prior to dry-in. You will inevitably need to do work at some point in the future and knowing what is in the wall before is very beneficial.
5. Laundry room - make it 4x bigger than you think. I'd like to find whomever designed ours so i can beat them with a split bamboo cane. It's 2 feet too narrow and royally sucks. To the point that I'll be doing fun remodeling at some point in the future.
6. Pantry space - the more, the better. I don't know why pantry space is an afterthought, but don't make it an afterthought. Do it right, do it big, you won't regret it.
7. HVAC - don't let the HVAC contractor run flex duct everywhere. I hate that stuff, it's the lazy way of doing things. Use rigid insulated ducts for your main runs with minimal flex duct going to registers.
8. If you put your water heater in the attic, may God have mercy on your soul for being scum of the earth. Put it in the garage (assuming you aren't going tankless heaters). They will fail, usually on day #2 of a 14 day vacation so that it has a wonderful opportunity to destroy your entire house.