Does your preservative have the bad smell? Some smell truly nasty and if you're refrigerating it anyway, you don't need the preservative if you use the FSG within 2 weeks or so. Optiphen smells pretty awful to me. So does Benzyl alcohol.
Essential oils and fragrance oils - look at craft stores, for example, can be added (not sure how much, others do this - I'd use as little as needed). Those would give a fragrance.
You can also make your FSG with herbs (which you'd strain out with the flax seeds). Rosemary is an assertive scent and adds shine, bay leaf might be good too - depends on your taste in aromas.