Hi
I have done a few such pamper evenings and find them a great opportunity to hand out business cards/leaflets and to give a client an example of what you can do for them, and discuss nail care.
15 mins is time enough for a shape n paint.... anti bac hand wash, nail shape with the file, base, colour and top coat. Also offer the same, but with french finish. I have basic nail art to hand also, such as a diamante or two to add a little sparkle, or fine liners or striping brushes to add some flicks, feathering or stripes, dotting tool for some little flower patterns etc...
It is difficult in the time allowed to offer too much, plus generally people need their hands free during the evening so are happy to have the shape and paints, with a quick dry top coat.
Have a good evening, all the best