Okay, a few things that could make this editor better.
-Click+drag functionality for when you want a lot of the same tile.
-Needs to be an indicator at the bottom of what tile you've selected, like a bright shiny box around your selection.
-Hotkeys, like for changing between bright and dark.
-You have way too many tiles because you've tried to account for every combination of foreground/background tile. You should just be able to select a torch, for example, and put it anywhere and have it automatically show up in front of whatever background tile is already there. Distinguish between foreground and background tiles. Have two different delete tools: one for fg, one for bg.
-There needs to be a way to convert your level to text, so that it could actually be taken and used in a game. This clearly has the potential to be a game level editor.