Since you mention that it is a demo that you are putting together, I would say the first thing is to think about who you want to impress with it, and what they may be looking for--
Are you looking for jobs? Ask your booking agent what the people he/she is pitching respond to--Sending it to record labels? Check what they are selling, and what they think will sell, then emphasize that--Will you use this to audition for a group or a show? They may be looking something entirely different that the others--
A tip on your repertoire--find your niche, and sell it--It is your image,and yes, there are still a lot of distinctions within the Scottish/Irish Traditional frame work--Do you emphasize sad songs? Funny ones? Are you wistful and airy, or are you earthy and gritty? Serious intense, or waggish and light?
Do you dress up in an tradtional costume, or dress it down and make it more mainstream?
I could ask a hundred more questions, but you should get the idea--when you make a demo, you are selling yourself, and it is easiest to sell when you let the listener know what you've got, and differentiate it from everything else that comes in the mailslot--