you can’t actually get more hidden smileys than what are coded into yahoo messenger

Full details for v8.0 smileys are here:
http://www.wackyb.co.nz/Yahoo_Messenger_version_8_Smileys/

or the complete history of all the smileys past and present here:
http://www.wackyb.co.nz/Archive_Yahoo_Messenger_Smiley_History/

If you are using v8.0 then get the YEmote Plus Smiley plugin which gives you full access to all the secret / hidden smileys as well as the std ones
“YEmotePLUS gives you access to ALL the secret and hidden Emoticons / Smileys quickly and easily, Multiple layouts let you organize smileys into groups and categories. Customize the layout/background colour with drag’n'drop smileys where you want them, even send your layout to friends running YEmotePLUS!. Click animated smiley to be insert automatically into your text. Full mouse over descriptions (and which versions of messenger Windows / Mac can see them). Right mouse button click to preview all smileys animating. New MSN Live mode switches to compatible smileys when chatting with your Windows Live Messenger contacts. See ‘info’ tab in plugin for more information / feature list. YEmotePLUS is a conversation plugin for Yahoo Messenger v8.0 and above, check screen shots and our website for more details on how to use plugins.”"
download here:
http://us.gallery.yahoo.com/apps/380/locale/en
support @ http://www.wackyb.co.nz/YEmotePLUS_Yahoo_Messenger_Plugin/

or you want to use shortcuts to generate the smileys check out DaveC’s Yahoo! Messenger Smiley Shortcuts
http://www.wackyb.co.nz/option,com_remository/Itemid,3894/func,fileinfo/id,13/

and if you need more practice using them check out this…
http://www.wackyb.co.nz/EmotiBlaster/