It ultimately boils down to the conditions of your campaign, and the rewards that you are offering. A few points to consider:
1. How many kinds of prints are you offering?
2. Are your prints your main reward, or are you also offering other items?
3. What's the lowest amount of backers that you anticipate having for this campaign to be successful? For example, if you run a $2,000 campaign, do you anticipate having 200 $10 backers that you need to send prints?
4. Where is your product being manufactured?
Some manufacturers can ship product directly, while others require that you come up with a shipping solution. It's quite normal for larger campaigns to make use of a fulfillment partner to ship out rewards, but many campaigns of all sizes opt to ship their packages themselves through the USPS.
As a practice, it is also a good idea to consider assembling an entire reward package before sending it out for fulfillment. Some campaigns offering mixed reward items choose to fulfill part of an order at a time, rather than all at once. (printed pictures through one provider, t-shirts and mugs through another). This can increase complexity for keeping track of which backers have received everything, and which backers still need to be fulfilled.
Full disclosure - this commentator works at BackerKit, a post-campaign platform for project creators.
This is just my opinion, but I believe there's nothing wrong with sending directly from the printing company or a Fullfillment organization.
I do think it's immensely important that you accurately describe what exactly they are getting, however. If it's described as original art and implied it's the original copy (i.e. the actual painting on a canvas) it makes sense it'd come directly from the artist.
If you're clear it's a *print* of the original, I may not matter either way. A signature on the art, a note from the artist, or packaging made with love are all nice to see, sure. It does help build connection between you and your supporters and community.
However, if it's described as a print and you can significantly cut overheard by shipping from the print manufacturer, I suspect the later is the better option. I don't think you'll get much negative flak if you take that option. It can potentially bring your goal much lower or make your product better, which I believe most backers would find most important.
It may also matter what your primary product actually is and how close artwork is to your main campaign.