I love these armwarmers. I wear them every chance I get. But it's getting warmer so the chances are running out! I knit them in the round and used a lace pattern I found in my stitch dictionary. The underneath part is stock. stitch. Here's some pics...

and a close up...
Edited to add the following pattern...I used US Size 8 DPN's and Worsted Weight Yarn (Red Heart Soft)
CO 30 (separate sts on DPN's however you want and join in round. I think I did 12 sts on 1st needle, 10 sts on 2nd needle and 8 sts on 3rd needle to accommodate the lace pattern
K1, P1 Rib for 8 rows
(Start Lace Panel...)
Round 1: *K2 tog, yo, K1, yo, sl 1, K1, psso*, K3, yo, sl 1, K1, psso, K2, rep * to * 1x, K rest of sts.
Round 2: K all sts
Round 3: [K2 tog, yo, K1, yo, sl 1, K1, psso, K1] twice, K2 tog, yo, K1, yo, sl 1, K1, psso, K rest of sts.
Round 4: K all sts
Round 5: *K2 tog, yo, K1, yo, sl 1, K1, psso*, K2 tog, yo, K3, yo, sl 1, K1, psso, rep * to * 1x, K rest of sts.
Round 6: K all sts
Repeat previous 6 rows until desired length... I did 7 repeats. On the last repeat of the pattern, do the following to make the thumb hole (Remember to alternate which side you do the thumb hole on for whichever hand you're making it for):
On 4th Row of pattern, BO 4 sts in the stock st. part (right next to the panel pattern) for thumb hole. CO 4 sts in 5th Row of pattern where you bound off in previous row. Finish 6th row as normal.
K1, P1 Rib for 8 Rows to finish off.
If any of this is confusing or weird, let me know.