The best thing to do is a Google search of "airstream renovations" and variations on those words. You will get a lot of interesting ideas come up.
For me, the easiest, most budget-friendly and most dramatic contemporary change I made were the lights. Look on ebay for the small 12v
"airplane lights". Also referred to by some as "puck lights". The wiring is already there for your current 12v
lighting system, you just need to phish some new wire behind the aluminum interior skin from those to wherever you want the new lights. I cut the holes with one of those core/hole drill bits. You'll need to install new switches for these lights. I purchased some basic 12v
dimmer switches (not cheap) but they allow you to create a cool mood-lighting effect. Just my 2 cents.