Shimmer is eyelash isn’t it and cosmic is more a ‘fur’ type? Not sure that would translate but you could swatch perhaps. I don’t know the other yarn sorry.
Perhaps look between the patterns on this site and see what you think about them ‘crossing over’ ok:
I was just looking at an old mag with a promo for this yarn: it was for a cushion cover, pattern code 5077. it combines cosmic and aran yarns with tassels at the corners. (from the picture its simply two rectangles of garterstitch holding the aran and the cosmic together, and the tassels seem to be all cosmic. the pillow looks to be the standard pillowform size- maybe 20 inches?). the promo also suggests using the cosmic for “comfy cushions, scarves, hats, and ponchos too”.
sorry I don’t have the actual pattern, but maybe this will give you an idea of how to modify some free patterns…