There are many artists posting their favourite pieces on the /r/art subreddit. It is also a good place to find images to feed into Dall-E for purposes of zooming out or uncropping. Dall-E fills out the image based on a marked area surrounding it. When building the missing parts, it will take into account a prompt and the original seed image.
The artists are often quite positively surprised by seeing their work expanded like that.
Most of the time I used a slightly modified version of the artist's given title as the uncrop prompt. Sometimes I specifically mention certain items in the prompt, like a tool or some clothing or a style.
Here is a selection of uncropped artworks. The original image is always on the left.