There are lots of free twiiter icons available on net, why not search best ones for you? and list those here. I found “485+ Free Best Twitter Icons And Buttons Part 1″ and i made list of all those collections for you.
Hongkiat says, “Catchy graphics are always better than plain text and they are easier to spot. If you are keen to increase Twitter followers, here’s a compilation of 100+ Remarkably Beautiful Twitter Icons And Buttons you can apply on your site.”
TwiTip says, “…Below are some links to places where you can download 181 different free Twitter buttons, widgets, badges and counters to use on your site (actually there are over 181 when you consider the different sizes, colors, formats that are available on some of these options).”
Twitter Social IconsSet of six social icons (Digg, Twitter, Delicious, RSS, Reddit & Stumbleupon) are free to use on your websites and blogs however you wish! Courtesy of Designreviver.