Things to think about
Your 90k/105k maintenance is approaching: Subaru maintenance schedules and new car break-in period- 2000 through 2009, links for 2010, 2011...
You typically don't need a FMIC with a stock TD04 turbo, assuming that's what you have. It won't really hurt anything... you'll just experience some extra turbo lag. As was already stated, try to take some pictures of the turbo and downpipe area.
If you're still on stock struts, those will probably be due for replacement in the near future.
The battery would normally be located right behind the driver's headlight, but it looks like it has been relocated - perhaps to the trunk?
Often when an FMIC is installed, the stock windshield washer fluid reservoir is relocated or exchanged for a vertical tube style piece. After looking around your picture, I can't see it either, so either it was deleted or the previous owner did a good job of hiding it.
The stock radiator is known to be a weak point in these cars, especially with higher miles. The end tanks are plastic and prone to cracking. If you plan to keep the car for a while, you might want to upgrade to an all aluminum aftermarket radiator, perhaps when you do your 90k maintenance.
Generally, cold air intakes and atmospheric-venting blow off valves are touchy subjects because they can cause the car to not run properly. Some aftermarket intakes cause the air to not flow past the mass air flow sensor in the same manner that it would in a stock car, so it can be difficult to tune properly due to different bends, turbulence, etc. Atmospheric-venting blow off valves, although they sound cool, cause the car to run rich between shifts and can't be properly tuned for. A recirculating bypass valve is generally the way to go. I can't really tell what kind of intake or valve you have on your car just based on those pictures... but if the car is running poorly, those might be two places to check out.
In pre-2006 WRXs, the stock up pipe came with a catalytic converter in it. Upgrading to a catless version is a safety mod as the stock catalytic converter can break down over time and send bits of shrapnel into the turbo and engine causing potentially catastrophic failure, so that's something to think about too.
It would probably also be important to get some type of protune on the car as soon as possible for peace of mind.
Otherwise, the car looks pretty clean from the pictures. Congratulations!
P.S. - Here's a very helpful link about different mods: http://forums.nasioc.com/forums/showthread.php?t=533787