Alpaca is soft and warm, but the yarn tends to stretch. I made myself a scarf in alpaca a while back, and it just keeps getting longer and longer. My SO needed a new scarf (the first one I knit him has disappeared; I figure it is in the back of a closet, invisible to the naked eye, because it is black), and despite my experience, I went with alpaca.
I purchased some brown and some tweed (brown and cream) yarn, thinking I could alternated them every two rows, but the brown overwhelmed the cream, so I used just the tweed. I thought maybe if I knit the scarf lengthwise, it might not stretch as much. That was a misstep as well, one that I could not determine until the whole thing was complete. Still, I like the result.
Yarn: Sanctuary Yarn, in 'Tweed'
Pattern: None. I cast on 300 stitches and knit in garter stitch until I ran out of yarn.
The yarn came from the Big Red Barn, where the owner raises alpacas. The colors are the natural colors of the animals; I believe the brown is from Louie and the cream from Babe.