Polish model Maja Salamon, after A Show, NYC, September 2015.
A net hair accessory + dress with a cheeky cutout (which sort of looks tennis inspired especially with Maja's sneakers). 
Recreate Maja's look (kind of):
Dress with little cutout — 3.1 Phillip Lim cutout knotted satin dress, Tomas Maier Denim cutout dress, BCBG cutout dress, Madewell cutout denim mini dress, Thakoon lace & eyelet dress, Goen J Ruffle cutout dress, Topshop striped bow midi dress, Suno cutout dress, J.W. Anderson cutout crepe dress, or Charles Youssef sculptured dress