I am the entire IT department for a private K-12 school. I also teach an accelerated C++ class to high schoolers in that lab over the summer. We have one computer lab with 25 PCs. Here are some of the things I've done or plan to do to make it a pleasant and productive work environment, in no particular order:
1) Have a good projector. Our projector does not support resolutions above 1024x768 and it can be a pain when the working window is needlessly smaller because of large static elements like the taskbar and toolbars.
2) Install in-ceiling speakers connected to the teacher workstation to distribute sound evenly. I recommend in-ceiling speakers from Monoprice.
3) Have a free-for-all shared network drive for students. We have three shared drives: one for students, one for all staff, and one for just office workers. This is probably one of the features that's easiest to set up yet appreciated the most.
4) Use centralized logins. At my school I have a passwordless "student" account with a mandatory profile, while all other accounts are roaming profiles with redirected folders. I've not heard any complaints about this. Students get the same desktop experience on every computer, and teachers love that their settings are shared between computers. I also offer (through the logon pop-up message) to create roaming profiles to students who want this feature, but no one has yet taken me up on this. Probably because no one ever reads that message.
5) Set up Fortres Grand Clean Slate or Faronics Deep Freeze on at least a few computers and configure them such that every account is an Administrator. There will always be students who'll want to install a legit program you haven't foreseen. Let them.
6) Keep software up-to-date. No one likes using Firefox 2.0 or MSIE 6.0 on locked-down PCs. Do this either through group policy (if you're fearless) or by reimaging PCs on student breaks. Reimaging works because everyone's documents and settings already live on the server.
7) This is controversial, but allow students and staff to attach any personal device to the network. We have a schoolwide wireless network, so this allows everyone to stay connected no matter what part of the building they're in. This has been tremendously popular at my school, and so far haven't had any issues.
8) Use standby. No one minds it, and it saves a huge amount of energy. Use something like Faronics Power Save Enterprise if you want fine-grained control, or just configure Windows power settings to go on standby after X minutes of inactivity. As a bonus, standby is also quick to reveal defective RAM. (Bluescreen, "hardware problem, contact manufacturer")
If anyone reading this is in Cedar Rapids / Iowa City of Iowa, I am an IT consultant and would love to implement this at more schools. :-)