To complement Violet ... is that the colour of your bedroom? or something you are wanting to put into the bathroom?
If the bedroom is violet ... how about a lighter shade?.
Go withs ... think of flowers, particularly irises ... other shades of violets/purples, deeper, lighter
White ... can help to keep it clean and fresh looking
Grey ... I'd be careful on that. For me it could become dreary all too fast.
Mustard ... can work really nice with violet
Pinks, rubies, burgundy, etc. .... again back to looking at flowers!