Wide format, the prototyping area is either side of the Photon making it easier to connect to the GPIO pins on the photon.
A USB A plug can be mounted onto the PCB allowing the prototype to be plugged directly into a USB power outlet (PC, Wall brick, battery etc.).
JST socket pads on the PCB bottom allow a standard LiPol battery JST socket to be mounted to power the circuit by a battery or external power supply input.
Diode protection on the JST and USB A plug prevent current flowing back into the USB or battery when powered by another source.
The Photons Analog inputs have 3v3 pull-up 1206 pads (PCB top layer) and pull-down 1206 pads (PCB bottom layer) to GND, this makes it easy to create a potential divider on the analog inputs for resistive sensors such as LDRs, thermistors, variable resistors etc.
7x 1206 pads top and bottom for SMD LEDs, capacitors, resistors etc along the top edge.
PCB bottom layer underneath the Photon has 1206 pads connected to D0 and D1 for I2C pull-ups.
1206 pads work well of 0804 components as well (they are actually easier to solder).