Put in a bunch of wiring for 'can' lights. They have some new LED pancake remodel pucks that are really nice and well priced. You can never have too much light. Add some wall outlets while your at it

Another thought is ventilation, you may want to add soffit/gable vents to keep air moving up there once its sealed off. As mentioned before, a retractable access ladder is a good idea and if you plan on storing anything up there (and you will), beef-up the trusses and add a floor but don't put the bowling ball collection up there.