Add Decorations, Lights, trees, reindeers, ANYTHING!!!
Light up the house as much as you want, make it beautiful!!
I acicdently did 2 lines of coloring on the Door/window/Line layer instead so please keep it in mind that you need to colour those lines in on a different layer!
Have fun and make it christmassy!!
(please don't change the lineart of the house though, You may add in a garden and decorations in the garden too)