As RydelFox has stopped uploading his concept art, I decided to make at least the various sprites available for viewing.
 
Here’s a collage of the various Espers in the game. Most are from G1 but others are not, like Sunshimmer being G3 but included to connect to Sunset Shimmer. There are a few little nods to G1 story as well, what little I know of it. For instance, Majesty had magic horseshoes that can turn her invisible, thus she replaces Phantom who casts Vanish on the party.