The booth is called Marvel Fine Art by Choice Collectibles Because of a weird licensing agreement, there is a limited presence of Marvel at Walt Disney World. That has included the Epcot International Festival of the Arts in the past. This year, there is finally a booth that is filled with Marvel artwork! You can find it at the entrance to World Showcase on the Mexico side.
If you’re interested in why Marvel isn’t more prevalent at Walt Disney World but is allowed at Disneyland, here’s an article that explains it better than I can.