Like Monroe I love Christmas and go a little crazy decorating for it every year. It's one of the many reasons why I loved his character so much. To actually own some of the pieces they used to decorate his place for THREE Christmas episodes... that was pretty much best thing I purchased out of all of the Grimm props. It was AH-MAY-ZING to discover that there were actually some of the Christmas decorations left on the last day. I dug through and found some awesome pieces and I was thrilled to discover I can place them all in various screenshots from the different holiday scenes! Some of the pieces I have were in all three of the Christmas episodes!
The three episodes were:
Episode 107 - Let Down Your Hair
Episode 308 - Twelve Days of Krampus
Episode 407 - The Grimm Who Stole Christmas
Season 1, Episode 7:

Season 3, Episode 8:



Season 4, Episode 7:

The other really cool item that I love is one of the light up ceramic houses that surround Monroe's train track. I believe it's also in each of the three episodes but it was hard to get pics of it in each ep.
Season 4, Episode 7:
I also have the mistletoe piece that hung in Monroe's hallway, right near the front door entrance. You can see this when Rosalee first comes home and discovers all of the Christmas decorations.
Season 3, Episode 8:
I also found a bunch of ornaments and other trim that was used mostly on Monroe's ceiling, but also to trim doorways and windows.
Season 3, Episode 8:


Season 4, Episode 7:

I also have a bag of older glass ornaments that I believe were used on the tree. They look similar to the vintage style ornaments seen on the tree, but I don't have clear enough shots of the tree to match them up.