hi,

i suggest u to use projection mapping type instead.. cuase u can choose spherical mapping from there.
even without it..
in layer texture node put a base color u want and upon that place your 2d image node and don't forget to adjust alpha gain value... to black.. default is gray which won't let your texture transparent.......... or some thing like this.....


if u put your scene here then i can tell u better.

c u

lala