So draw a small picture (128x128 pixels is ok, 256x256 has better detail) and put in folder "objects/my_objects" Make a material file like this

Recycling another material file (open with notepad or similar) and renaming it (save as a .material file not a notepad ect file) makes it easy.
Open object maker, Mesh tab, type "flatplane.mesh" without the " symbols and press "add new".
Should find a tiny little postcard thing appears, enter the "MyMaterialNameHere" name (whatever you called it, probably "welcometotundratown" in your case) in the material text thingy in the object creator and it should change to what you drew in the small picture, scale it to suit your tastes.
You may need to distribute the material file with the map to people who visit it, i haven't quite figured out how to package everything into one neat little file yet.