LOA 4 - Accompaniment Playing Study 4

Hi David,

I am attempting to get some backing rhythms and fills together to accompany 'I Want You With Me'. No problem with the rhythms for backing the vocals as it's straightforward to work out the 1st, 3rd and 5th notes for each of the I, IV and V chords. I am struggling to understand what notes are 'allowed' for the fills. Should I be playing only notes from a specific scale or does anything count as long as it sounds right?

Thanks,

Mark.