1. As mentioned you can fix a Picture to the Map, thatway the Lanternpost would be always above the Player. Or you use Parallax Mapping Plugin.
OR
2. Char sheets can have any size, put your lanternpost on a charsheet which got the correct dimensions
Make it Priority "same as characters", than its shown above player if he is behind it, and below player if he is infront of it. Problem with big stuff is when map is scrolling those event graphics suddenly pop into existence, so you would need additionaly scripts to make it work without bugs.
OR
3. Every Map can have its own Tilesets, you could put the lanternpost on one of the B, C, D or E Tilesets
and Map it manualy. In Database give the Lanternpost Tiles the passability setting "star", than its above the Player.