Possible to limit the amount of maps a player can make? Like if they attempt to place more than 5 maps, it would say, "You have more than 5 maps, please remove some to place more." Or something like that.

Also if possible, allow other players to remove images instead of using the command, just like clicking on the image directly instead.

Also if possible, allow other players to remove images instead of using the command, just like clicking on the image directly instead.

This feature is already implemented, it's called image items and can be used through the /image give command.

Possible to limit the amount of maps a player can make?

On a similar note, this might be better achieved by not letting players use the /image place command and instead give them a limited amount of image items.