...I viewed your site on a number of devices but the biggest file it showed me was 1024 pixels wide...
While reading this thread on my iPad (with Retina resolution), I made a screen shot of one of synn's images (Rainbow City) from his website. It measured 1645x1234px. I can guarantee you I can print it as a 24x30 canvas beautifully, using an up-rez software, and sell it in art fairs (I won't).
For some of us selling our own prints at art fairs, a frequent question is do we have a web site. What is preventing a visitor to then go home, download one or more of my images and print it almost the same size I am offering, for a fraction of the cost?
Then again, if you have no concerns of that or similar kind, do upload the largest size you have.