The How to's of using IMVironments...
Pop yourself into an IM converstation with someone and hit the IMViroment icon...


you'll be presented with a the selection window..

where you can choose from the previews, once you've made your selection hit OK and you'll be taken back to your active IM window where you can start talking.. simple :-)

IMVironments ™ IM Preferences..
can be accessed via Login, Preferences...

If you just don't like them then uncheck Enable IMViroments.
Under When I receive and Instant message you can select from either Show IMVironments only from people in my friends list or Show IMVironments from anyone.. I guess if you don't want 'strange' IMViroments showing up then your best to check "..only from people in my friends list"
The check box beside Show IMVironment status notifications is this..

it lets you know what IMViroment the other person has choosen.
When I Open and Instant Message Window with a friend is quite nifty as if you wish to it will Remember the last IMViroment that you used with that particluar person and lauch it!

now if the person your trying to share an IMVironment doesn't have v5 of messenger this is the error message you'll see...

Links...
[Yahoo! Messenger - IMVironments™] (Yahoo! Site)