Please post code correctly in the forum.
… with TAB characters replaced with 2 space characters.
Because SketchUp’s Ruby cannot find them.
The location on disk of the current interpreted file is got with the global __dir__ method.
You have the icons in a subfolder named "Example Images".
You can build a full path to the files using File.join method.
cmd.small_icon = File.join(__dir__,"Example Images","Cabinets_small.png")
cmd.large_icon = File.join(__dir__,"Example Images","Cabinets_large.png")
[I suggest shorter descriptive icon names like: “Cabinets_small.png” and “Cabinets_large.png”]
You might also be able to use the block form of Dir::chdir method (which restores the previous current directory when the block ends.)
Dir.chdir(File.join(__dir__,"Example Images")) do
cmd.small_icon = "Cabinets_small.png"
cmd.large_icon = "Cabinets_large.png"
end