Originally Posted by
daaxix
Hey man, do you see that big hole on the top of the front fork (called the crown)? Before you do anything else, you NEED TO PUT A BRAKE THERE!
A) It's not
your bike, so the OP "needs" to do nothing.

While not as effective as a front brake, you
can stop a fixed gear without one.
B) (to the OP) You should easily be able to fit a pair of SKS P-35 fenders in there without any trimming. Even that rear clearance looks fine. I've got a late 80's Trek 400 with a similar looking amount of frame clearance and I've got 28mm tires and P-35 fenders. It's a bit of a tight squeeze, but I've managed to keep about 3mm fender clearance from the tire. With 23s on there, you should have well over 5mm clearance all around.