I have not seen such problems in the rendered output.
I've learned with different systems over the years that imported photographs might lose resolution or get "stretched".
What I try to do is make sure the pixel size of the imported photograph is the same as the size that I want in the rendered output.
I do that in Photoshop, either by resizing the image or padding it with a border.
For example, if you intend to produce 1080 x 720 output, create an image background of that size and paste your pictures on it.
If your images are larger, use the photoshop resize function to make them 1080 x 720.
Nikon D5100
Dell Latitude E6510 for dev/editing
Dell XPS 8500 for production
4 Core i7 M620 2.67Ghz
8GB ram
Win 7 professional, Ubuntu 12.4
PowerDirector 10 Ultra
Virtualized Ubuntu Srvr