I was talking to a flower arranging expert today and mentioned your question. Flowers that would have been available, both wild and cultivated, in Elizabethan times and in season would have been things like Dianthus, Sweet Williams, spray carnations, Aquilegia, Nepeta (cat mint), foxgloves, Tansy and forget-me-nots. The Elizabethans were very keen on fragrance to disguise the not so wholesome smells of their every day lives so things like Rosemary, Lavender and very old rose varieties would have been popular. For foliage, native ivies, fennel and yew and box would all fit in well while containers could be of pweter, rough earthenware and even silver. Hope this gives you some ideas.