Goblins are usually portrayed as ugly mythical creatures that range in size from the size of a hobbit or dwarf to a human. They are usually green or brown and their chief characteristics are: mischievous, unintelligent and somewhat petty. For this reason, they are not among the high ranking powers of "evil." They are more henchmen to the more powerful figures. They are also closely related to orcs.
In the role playing game, Dungeons and Dragons, goblins are some of the lowest level monsters that one will face. They generally fit the above description.
You could be really different and bring back their old name , the 'hobgoblin.' Look in Shakespeare for inspiration - Puck was based on a goblin. They are often mischievous, not often truly malevolent- with big ears. Puck may have been based on another legendary character called Robin. Quite often the goblins are given lots of hair and are small in stature. They have been portrayed as great jokers, though often their practical jokes can verge on the slightly dangerous. Maybe that is why they have become associated with bad luck coming or trouble. Look at the quote from Ralph Waldo Emerson 'a foolish consistency is the hobgoblin of little minds.' I have furnished a link to Puck below - also checkout his historical context.