If you have Gleamclub, you can use the emoji in a sign by typing a colon : the unicode : then another colon. Not all symbols will work. Luca made a post with the ones that work in Boundless and there were some added recently (will add to the bottom of this post)
So for example, to get the globe above, you would type :1F310: in the sign
For these, you can type the object name 
is : colourspray :