Polarr is an offline photo editor app for Chrome OS. They developer describes Polarr as a powerful, versatile, and elegant photo editing tool. He also mentions it can handle jpg's up to 30 MB in size, as well, as loading multiple photos into one session.
Polarr in many ways reminded me of the Photoshop Editor without the toys. One big advantage to Polarr is its offline capabilities which if important for when wifi is touch and go. I would argue some of the features on the right panel are more advanced that the Photoshop Editor. Polarr is definately worth taking for a spin for your basic and more advanced photo editing.