Jai Srimannarayana!
Vishwakse:na and Vina:yaka were not one and the same. Vishwakse:na appears just like Lord Na:ra:yana Himself. Colour will be ordinary not blue. Along with Sankha and Chakra he will be holding a long stick in his left hand and showing index finger with right hand, to fear all the evil powers. Several elephant headed (gaja mukhas) gana:dhipathis are in his force, to obey his instructions in removing the hurdles of Vishnu devotees. Vishwak Se:na is the whole and sole to look after the administration of the entire Universe and also the Paramapadam. Here is a verse says that

“vande: vaikuntta se:na:nyam, de:vam su:travathi:sakham |
yad ve:thra sikhara spande: viswam e:thath vyavasthitham ||”

Whatever draft he prepares with regard to running the vibhuties or Universes, will be accepted by Lord Srimannarayana, without any alteration or addition, it seems. A:lawanda:r Stho:tram reveals this in its verse
” priye:na se:na:pathina: nyave:di thath, thattha:nuja:nantham uda:ra vi:kshanaihi”.

This is the greatness of Sri Vishwak Se:na. As Gajamukhas are somany in the Pariva:ra of Vishwak Se:na, in some occassions if devotees worship a Gajamukha in the place of Vishwakse:na, as a representative of him, will also be accepted. Because all the pariva;ra:s pass on the result to their boss always.

But then that Gajamukha will be having four hands with sankha and chekra and also with U;rdhwa pundram on his fore-head. There may not be rats as his chariot. These Gajamukhas are not mu:shika Va:hanas. We are sure you understood the subject.