Pixel2Canvas does a good job (I'm a photographer by the way so I only recommend a couple to people)
Canvas On Demand as well does a good job. Look for sales, like both on FB or whatnot.
My absolute favorite is Simply Color, but you have to be a pro for them, so for my clients who want canvases made (not through me) I recommend the two above.
I hope that helps. Yay on having some big photos printed!! Go bigger than you think as they won't have a mat or frame around them. TRUST ME I did a 11x14 one at first and I was like oh that is tiny! Go big or go home ;-)
Also you can size it out using painters tape as well to see just how it will look on the wall size-wise.
__________________
|