Thirties fabrics are saturated pastels. Several colors are indicative of the Tirties--that NILE GREEN, APRICOT, and DENIM BLUE in your butterflies. I think I would use a small Thirties repro print.
Thousands of Bolts has some very pretty Thirties prints, many pretty blues, for $4.25 a yard, quilt shop quality.
http://www.thousandsofbolts.com/inde...=45&hidesbfq=0