Timothy, Click YourFreeAudioBook.blogspot.com for The Audiobook How to Sell Art to Interior Designers

Hi Timothy, I apologise for the tardy response. Nature photos are often used by IDs as long as the image fits the project they are working on. That last is the same response I’d make for any artwork regardless of medium.
There’s no reason not to start a new business at age 78, particularly because you want to be out and about. From my perspective at 87, you’re still a kid.
I think the only Internet sites that handle everything from printing to fulfilling a finished product are ones like Fine Art America, CafePress and Zazzle. Barney may know others. Keep in mind that you must drive traffic to your “storefont” if you want to sell anything. Also, once there, your potential buyer can see similar art by hundreds of others with the click of a mouse.
You may also want to submit images to Stock Photo sites. There are many. Just Google Stock Photos.
When I had an Ad Agency we bought the rights to use photos in some of our ads. Right to use is what you are selling. You can put the same image on all of the above unless a “seller” demands exclusive use and you agree.
If you’d like a more in depth answer, please consider the new audio edition of How To Sell Art To. Interior Designers.

You’re welcome. Get a body of work together and get started marketing. Action is almost always better than waiting for perfection or for the right time.