Just to see how the Instagram stuff compares to images from other sources, I pulled a couple images from my Flickr account as well. Predictably, the Flickr stuff looks technically better than the Instagram images, but the filters certainly help even the aesthetic playing field. But, I guess that's the point. Also, by adding a white border to the Flickr images, it helped them blend into the collection a lot better. Personally, it would feel kind of awkward to have an inconsistent mix of aspect ratios and overall print quality, but that might not bother you.