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.
A Little Bird Told MeInspired by Twitter and other vector designs. By mattknow
Create a Twitter Style Bird MascotTutorial on how to create a Twitter mascot for your blog or website.
Twitter IconCreated by PhireDesign.
Free Twitter Graphics: Here are some free graphics to put on your site for that purpose- just place the image on your site and link to your Twitter profile.
Twitter Birdy Icon: Cute birdy icon created by Kailoon. Available in transparency PNG format.
Free Twitter Icon Set: This set contains 4 different poses of the Twitter bird. Both PNG and PSD versions has been included in the .zip file.
Pracktika Free Icon Set: Designed by DryIcons, released by Smashing Magazine. Available in resolutions 64×64px, 128×128px and 256×256px, in 32-bit transparency PNG.
Web 2.0rigami: Twitter icon, origami style.
Feed & Twitter Monster Icons: Feed and Twitter icons as monsters.
Twitter icon for a fluid app: Really big Twitter “t” icon.