Random Image

Array
(
    [per_page] => 15
    [page] => 1
    [extras] => original_format,url_sq, url_t, url_s, url_q, url_m, url_n, url_z, url_c, url_l, url_o,o_dims
)
string(6) "square"

Thumb_size options only square,thumbnail,small,medium,medium_640,large,original

see function buildPhotoURL()