Those are switch block graphics. In the original SMW, they show up in switch palaces to say "the power of the switch you have pushed will turn
You can either build your message around them, or have SMW not treat your level as a switch palace. To do the latter, go to "Overworld --> Change Special Message Levels" and set the switch palace level to numbers you're not using.
(also, your switch graphics seem to be broken. the flattened switch looks like two spinies instead, which isn't nice.)