I often see photographers on forums saying "I'm thinking about getting a canvas printed - is this photo good enough?"
There's a very simple rule here: If you like it on screen, you'll LOVE it on canvas.
Canvas is wonderful. Nothing beats a great photo enlarged on your wall.
I'm pretty casual about it, of course, because I print photos on canvas every week - it's a small part of my small business. All the time I see nice little photos become wonderful big canvases; and I always enjoy the delighted responses of my customers.
These customers aren't pros - they're just regular people shooting with regular cameras. Heck, sometimes the photos are technically terrible, but they have deep significance to the owner, and that's what matters - memories, not megapixels.
The funny thing is, the more you know, the more you worry. My customers don't care if something doesn't adhere to the rule-of-thirds, or if there's a limb chop, or even if the focus is fuzzy. They order with their hearts, not their heads, and that's the way it should be. But photographers, on the other hand, get so bogged down in technicalities they forget what inspired them to be photographers in the first place - the love of a wonderful capture. So, again I say - if you like it on your screen, you'll love it on your wall.
If you've never had one of your photos printed on canvas before, don't hesitate. Pick one that makes your heart melt, and just do it! You will adore it.
I should discuss size for a moment. Many people ask "how big can I print this on canvas?" I want to reiterate something I've said frequently before:
The whole "what's my size limit" thing is a recent phenomenon, and is frankly silly. Did we ever limit ourselves to 35mm prints when we were shooting with 35mm film? Of course not. There's a lot of myth surrounding enlargements - people seem to think that enlarging a photo will mysteriously make it worse. Enlarging a photo doesn't make it worse, or better - just bigger. If it's a great file, it will be a great photo. If it's got some flaws, it will have those exact same flaws when enlarged. Not worse - the same, only bigger.
The great thing is, canvas is a pretty forgiving medium. It's fairly coarse, so noise is well-hidden. It requires a lower print resolution, so your megapixels stretch further. And of course, it's designed to be hung on a wall and viewed at a distance, not held in your hand like a small print is. I've written some more advice about this here: How big can I print my photo?