Tactile depth --- velvet, velour, quilting, pleating, furry or fluffy textures, slubby silk or smooth satin, braided trim, lace...anything that suggests a touch of luxury or coziness --- and that reminds me of cabled knits now.
Shine (even subtle) --- needn't be sequins, could be brocade like Diana suggested or even a slightly shimmery thread running through a knit or a tweed, or just the natural sheen of satin or velvet
I find stripes (not just candy-cane colours and widths) and larger dots festive because they remind me of wrapping paper, probably.
So do byzantine/baroque motifs, for the same reason --- they're common in brocades, but also now in other printed fabrics.
In terms of colours, doesn't have to be Christmas colours, I think --- anything that reminds you of a box of individually wrapped chocolates (usually jewel tones, but also pale shimmery pastels)... or colours reminiscent of flames
Shapes --- short of santa and reindeer and candy canes and gingerbread men, you could consider stylized snowflakes or stars or snowdrops for jewellery and accessories, as well as paisley, tree prints or poinsettia-type patterns, some of the more seasonal animal patterns (hares, owls, fox, mice are not 'traditional festive' animals but are wintry in some ways) or intricately patterned round beads (bauble-like, but not obviously Christmas ornaments)
Some fabrics are distinctly wintry in association, like plaids and tweeds... and again, brocade and velvet.
