Button part of the plugin script:
local button = toolbar:CreateButton( "Terrain Creator", "Open Terrain Creator", "http://www.roblox.com/asset/?id=145723965" )
Error:
18:54:23.304 - Unable to load plugin icon. Image may have an invalid or unknown format.
When dealing with decals on ROBLOX, you need to -1 from the original URL to get the asset id, if you put http://www.roblox.com/asset/?id=145723964
(one less) then it'll work!