Very sweet idea! (: I think a masculine while modern design could incorporate shapes and patterns, like squares, stripes, rectangles, anything really! Try mimicking pillow designs you’ve seen before while incorporating your own feature, like lacing the edges with ribbons. Or maybe use the ribbons to make the shapes? Also, is there something your boyfriend is really into? Like a band, sport, etc? Just an example, but let’s say he plays guitar, you could transfer an image of a guitar onto the pillow, maybe make the edge of the guitar stand out by sticking ribbon around the edge. Or a cute/unique, maybe slightly cheesy idea, would be to transfer an image of you and your boyfriend onto the pillow. Just a suggestion. ;D