i think shaving brush is a calcium hog, like halimeda.
i got mine from other reefers. i have some of the grape kelp growing in my refugium.
there is no reason why you couldn't use these in your duisplay, except for the chance that it might get out of hand and overrun the tank.
also, some of the algae you are interested in might be a good food source for whatever inhabitants you are planning to keep, and that would be another reason why it wouldn't work in the display.
i don't know about other tanks, but in my tank, plant matter doesn't last very long.