Wait until at least Parent's Weekend to consider bringing out a desktop computer or Xbox, they go back and forth what seems like every year on those rules at the wing level which leads to some confusing variations at the squadron level. Regardless, you'll be able to have either of those after 4* year if they restrict it during the first year.
I would really suggest waiting to bring out anything for gaming until after 4* year, to be honest. Unless you have a great GPA and are pretty well balanced in all your cadet duties, gaming can be a huge distraction and has put more than a few doolies on acpro that first year. Another option, if you develop a good relationship with your sponsors, could be to bring it out to their house. That way, you're not tempted to use it during the week, but you do have an option to blow off some steam on the weekends.
As far as personalizing your room, that depends too. You can put pretty much whatever you want on your bulletin board behind your desk, so a lot of people put up pictures. When I was about to graduate, they were going back and forth on whether the upper 3 or upper 2 classes could use their own bedsheets (everyone uses the same comforter during daily inspections, though, so it's not like you can be that unique.) You might be able to put a state flag or something on your wall, but that's about it as far as decorating...there's a limit on personal items that you can display based on your class year, so a digital picture frame is a pretty solid idea.