What are you retailing? What services are you offering? Who are your target market - older ladies? Students? Mums? If you are thinking of things to buy, make sure these appeal to your ideal client and link to the services you are offering. Add a little handwritten note with the gift to link with a service.
Purse mirror to admire brows, mini cuticle oil to maintain their manicure. Shopping trolley token with salon logo on saying book online, sample size lip balm for all the kissing compliments they'll receive after their first visit, Embroidered lavender bags - perhaps with a decal of your business card (enclose a sliver of fragranced soap to help the smell last) and note saying we look after all your delicates, spectacles wiper cloths with decal of business card on - suggest they are for sunglasses and remind them to book their pre holiday treatments.
Offer an "if you can't wait" experience bag - make bath bombs and pop into organza bags; tea lights - perhaps make your own fragranced ones or if you have retail fragrance candles get some matching tea lights as giveaways, include samples of your retail products to trial: face masks, hair masks, sachets of various lotions. You could make your own give always - buy a job lot of mini pots off eBay and decant from a professional size, (enclose an ingredient card,)
Don't forget to put your menu in a cellophane bag with a few sweets, wrapped chocolate, or an individually wrapped tea bag and a handwritten note about taking the time to choose their first treatment.