Currently* in the default style* users are only given five static IM fields to utilize (ICQ Number* AIM Screen Name* MSN Messenger Handle* Yahoo! Messenger Handle* Skype Name). Those five IM applications are probably the most used ones in the world* however since vBulletin is used by so many different generes of community there are many applications that are simply disregarded due to the current method* such as Xfire* Steam and many others.
I propose that drop-down boxes that contain at least the top 10-15 IM applications* replace the current static fields that are in place. This gives the user a much greater choice and more flexibility. Then the forum administrator can alter how many IM fields the user is allowed by default (possibly five or so) and can very easily add custom IM applications to the list* along with a logo* with very little effort via the ACP. I have included a quickly photoshopped version of my proposal below.