Beetlejuice is a Halloween film character with enough enduring popularity that it is instantly recognisable. You might be better off making your own costume in order to really stand out, and this shouldn’t be difficult. Beetlejuice has a ghoulish but menacing appearance, and he strangely manages to look sloppy and stylish at the same time. If you can strike that balance you will easily pull off the character.
Wearing a suit that has black and white vertical stripes will work well in a Beetlejuice costume. Either wear a messy and longish wig or make your hair look similarly messy and longish. The makeup is the most important part of the costume, and emphasising Beetlejuice’s extremely pale skin and the pronounced dark area around the eyes is important. These aren’t just dark circles: these are dark areas that almost look like eye patches.