THE VERY FIRST THING when choosing a period frame is to find a fine art framer. Fine art framers will have a selection of samples to match the historical styles of the four main European art-producing nations: Italy, Spain, France and England.
If you cannot find such a framer locally, jot down the dates and country of origin of your art to see if there are frames that match the period at a public gallery. I would suggest visiting the European collection in a public art gallery and closely observing the frames. Then visit your framer to look for similar styles.
Canadian consumers will readily find French, Italian and especially British picture frames in their local framing shop. American consumers, on the other hand, will find French, Italian and Spanish with no hint (because of the Revolutionary War) of British frames.
Prior to 1900 frame design was based on a repertoire of heavily decorated styles developed during the Italian Renaissance. From 1900 onwards frame styles were essentially the substrates of these heavily decorated frames with the ornamentation stripped away. It was the 1930s Art Deco style that added angular shapes to the framing catalogue.
A mix of these styles travelled into the 1950s, where classical framing, which is based on a compilation of three elements (plate, lip and cap), gave way to two elements (plate and lip) in order to achieve the modern look. The illustrations are typical examples of classic and modern frames that you will find at your framer or in public gallery collections.