Who sleeps in this room? If a young person, lavender pom poms or fringe would work at the bottom.

You could also shorten them so that the hems hang just below the window sill.

You could hang them lower if there was a valance covering the top.

Typically an additional band of fabric would not go on sheers, that's your problem .... that type of band of fabric would go on the actual curtains that would be hanging over the sheers. Sheers aren't curtains, so I'd fix that problem. It looks like you have a blind on that window so these window treatments are just for looks? If that's the case, then I would hang a double rod (if you want to be able to actually pull the curtain panels over that window) ... hang the sheers on the back and get curtain panels in a solid color to hang on the front rod and then get put tie backs on the walls to drape both the sheers and the curtains over. That way no one will ever know the sheers are too short and you'll only see the lovely sheer part as it drapes over the window. Or do the same thing on one rod (if they really are only for looks and won't be moved) ... put the sheers in the middle and the panels on each end and drape them over a pretty tie back mounted on the wall.

I don't know if it would cost more than replacing them (I'd look in thrift stores for lace tablecloths or runners for a source of trim), but here are some ideas:

A complementary lacy trim:

I like the ideas so far, but yes, what is this room used for? And what type of person (age, gender) is using this room. You definitely have a lot of creative options, don't feel defeated!