Regency decorations, in most respects, were not all that different from ours today. A Christmas tree was a rarity, becoming most popular thanks to Queen Victoria, although the wife to the Prince Regent, Catherine of Brunswick, was reputed to have brought the custom from her native Germany. For some reason the idea did not catch on. However, the concept of greenery inside the house is an ancient one. The emphasis was on holly and mistletoe but pine branches or other tree limbs were acceptable. Ribbons, handmade ornaments, fresh fruits and nuts, and tiny candles were nestled within the branches that draped over mantels and banisters or were twined into hanging boughs. I am NOT recommending you use open-flamed candles but that would be the authentic way to do it!
Rather than a tree, a large hanging bough would be the household centerpiece. The spherical shaped Holy Bough dates from medieval times when it was suspended above the front door, decorated with symbols of the nativity, and blessed by the local priest. A kiss or embrace of friendship under the Holy Bough was a sign of peace to all visitors. The expressed purpose was to symbolize Christ as the Giver of Life and peace, but the stealing of kisses eventually became the main draw, especially with the inclusion of mistletoe.
If you are so blessed to house a massive wood-burning fireplace then you must have a Yule log (or clog, as it was also called). This custom is extremely ancient, and extremely pagan being attributed to the worship of various sun gods. Somewhere in the 4th century the early Christians adopted the idea as a symbol of Christ as the light of the world.
Concepts continued to vary throughout the centuries and cultures until Queen’s College, Oxford, incorporated the Norman Yule Festival as part of their Boar’s Head Feast in 1340. That effectively established it as an integral part of Christmas tradition. It has only been in very recent decades that the burning of a Yule log has lost favor, probably due to the advent of electricity and fewer fireplaces.
If able, find the largest log available of hard oak, dress it with wine, oil, and evergreen leaves, gather round and sing carols as it is lit, keep it burning perpetually through to Twelfth Night, and be sure to save the residual cinders to use as kindling next year. It will bring your house prosperity and good luck, as well as protecting from evil spirits. So say the Celtic Druids and who wants to argue with them?