It rather depends which senses you are trying to stimulate and where the garden is to be located. Will you be planting in raised beds or at ground level?
Woolly lavender smells gorgeous and is nice to touch because it has furry leaves. There are a lot of different lavender varieties that will all smell beautfiul when the plants are touched. They do need to be in a sunny location as do a lot of the herbs. Mint (several types, all different scents), rosemary, sage, thyme. If you want sound instead of scent then go for grasses that rustle in the breeze. Pheasant tail grass looks good but there are a host of different ornamental grasses to fill any niche.
Touch - grasses such as Pennisetum alopecuroides ‘Hameln’ for their soft flower plumes; non-spiky succulents; woolly thyme
Sight - different coloured heucheras
Sound - bamboo (best in a pot, not in the ground); plants with seed pods; a small trickling water feature
Smell - honeysuckle; star jasmine; choisya; sweet peas; chamomile; rosemary; chocolate cosmos; lemon scented geranium; if using mint keep it in a pot or else it will spread everywhere
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Taste (strawberries, etc)
Touch (interesting textures such as lamb’s ear)
Sight (colourful flowers - zinnias for example)
Sound (grasses)
Smell (herbs)
Touch - grasses such as Pennisetum alopecuroides ‘Hameln’ for their soft flower plumes; non-spiky succulents; woolly thyme
Sight - different coloured heucheras
Sound - bamboo (best in a pot, not in the ground); plants with seed pods; a small trickling water feature
Smell - honeysuckle; star jasmine; choisya; sweet peas; chamomile; rosemary; chocolate cosmos; lemon scented geranium; if using mint keep it in a pot or else it will spread everywhere