In the trading card art scene, it's not uncommon for an artist to want to offer playmats or prints of their art. Much of TCG art is either square or 4:3 aspect ratio, so the art sometimes loses a great deal of content when zoomed-in enough to fill a 16:9 playmat. That's where I come in!
Art extensions are always done with permission from, usually at the request of, the artist. If there are other license holders their approval is necessary as well. The artist and/or license holders (usually WotC) work with me to develop the concept, give feedback on progress and approve the final extension. All of the below extension examples have been reviewed and approved by the art direction team at Wizards of the Coast.
Goblin King, Original by Phil Foglio, Extension by Vianki Bruenderman
Swords to Plowshares, Original by Kaja Foglio, Extension by Vianki Bruenderman
I have described this as "collaborative and approved art forgery" before because... well, that's what it feels like! A great deal of time and effort goes into matching the original style, creating or modifying digital brushes to match original physical media techniques and brush strokes, as well as generous use of photo-composting software to result in a (hopefully) seamless extension of the original art.
On the question of AI..... while I do utilize some older tools, like content-aware, in most cases they will get me less than 20% of the way there, depending on the original art. Generally AI is a basic tool, not a creative tool, and never worthy of a final product. A bit of healing-brush, some fancy work with separation frequency, or using content-aware to fill in the bleed is helpful, but most of the time I have to do these manually. The result is simply better.
Art Alterations
Similar to Art Extensions, I've had the opportunity to alter art for a theme or event. These were done while working at Wizards of the Coast and, among other pieces, may still be found on their website.
I wish I had more examples... Sadly, I was under NDA while working at WotC and do not have my original files. If I come across more in the public webpages, I will add them here.