Ventrexians normally don't celebrate Christmas, so no. There are a number of native winter holidays on Ventrexia however, the biggest of which is Kalmûn Lyte, a celebration of the ancestors. It's similar to Yule, Diwali, or Día de los Muertos. Great parties and feasts take place as people gather to celebrate the lives and accomplishments of those who passed on. It's a 30-day season of festivities meant to encompass the coldest portion of the long Ventrexian winter. While gift giving as a tradition did occur, it was usually for small trinkets or offerings to shrines for ancestors. The practice did escalate after first contact with humans though.

1. Depends on what you mean by "open to ship". If you mean with your own characters, I'm mostly fine with that (I'd maybe like to see whatever you make though), as long as you don't erase the characters' identities in the process (don't ship gay characters with the opposite gender, etc). Generally I'd prefer if you asked me about it beforehand. If you mean shipping with other characters of mine, I would ask first, as the relationships each character is in is where I'm most comfortable, but there are a few exceptions.
2. Unless you are an of-age friend, any NSFW of my characters must be made with my verbal consent or commissioned by me. I will not tolerate minors drawing NSFW of my characters, and if you do you will be blocked.
3. SFW work of my characters is 100% okay, as long as it complies with my wishes regarding shipping and their identities.
4. Minor blood is fine, but full on gore is a hard NO from me.
5. Headcanons are fine, as long as they don't contradict the character or my own headcanons.