The photo "editing" in Google+ leaves a lot to be desired. Currently you only have the option of six effects relating to exposure, contrast, and color. Lucky for us Google Plus is built on current products that are fully functional in their own right.
What is Facebook photos without Facebook? Nothing.
What is Google+ photos without Google+? Picasa with Picnic integration!
When you upload a photo in your Google+ Stream it is stored in a Picasa album called "Photos from posts". Those photos are the exact photos that are displayed in your stream. When you edit that photo, the photo in your stream will change accordingly. If you want to get rid of red-eye, crop, add effects, sharpen, rotate, etc. you can edit that Picasa photo with Picnic.
To edit your photo with Picnic just find the folder in Picasa's Web Albums then go to the picture you want to edit. You will see Picnic's logo (a green hill, blue sky, and cloud) in the center of your screen near the top of the page, just below the upload button. Click that and you will be on your way. Once done, save your changes by clicking "Save to album" at top right and choose to Replace the photo. If you create a new version it will not link to your Stream.
Have fun editing!