It looks different because the pictures you've seen include the conformal fuel tanks.  These are large blisters along the fuselage above the wing intended to increase internal fuel volume.  The base of the vertical fin also has a large blister which houses new avionics, and most aircraft in the sries have the new "big mouth" inlet.  All these items make the aircraft "look" different, but the actual planform, configuration, and primary structure have not changed all that much.

The blisters add a lot of drag, but the new -29 engines (29,000 lbs thrust, either GE or P&W) more than make up for it.  The block 60 version (now called F-16E/F) has a 32,500 lb thrust GE engine.  The -29 engines can have either the "big mouth" inlet or the conventional inlet, but most customers have opted for the big mouth.  The -32 requires the big mouth.

As for avionics, block 50/52 avionics are much upgraded relative to the block 40.  A big plus of the system is a helmet mounted cueing system which allows sensors and weapons to "look" where ever the pilot is looking, and permits high off-bore-sight missile engagements.  (this latter item requires the new AIM-9X, IRIS-T, or Python 5 missile.)

The F-16E/F (formerly block 60) includes an AESA (active electronically scanned array) radar as well as the previously mentioned -32 engine and other avionics upgrades.  The AESA radar is a HUGE improvement for both air to air and air to ground missions.