Yes I did that while applying online to MPNP. I uploaded photos of few of my documents like Transcripts & ID cards. My documents were considered just fine & I was able to get MPNP nomination without any issues.
Just make sure that your photos are clear & easily readable & you are using a good camera instead of a cell phone. Afterwards, I used "Microsoft Office Picture Manager" to auto correct my photos. There are many online websites too with which you can further enhance them.
I hope that helps.
Regards