The Twitter icon is a little blue bird. Presumably they used a bird as they 'tweet'
Tjetz is a famous twitter icon .
Your header is the picture behind your icon and bio. (Your icon is like your profile picture)
Save a gif to your computer and upload it as your profile picture on Twitter.
You can't copy and paste images on Twitter.
You have to be a translator and contribute to translate parts of Twitter into other languages.
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If you have a custom icon you can simply upload it where you would normally upload your display picture.
Twitter doesn't store a "history". You can delete a tweet by hovering over it and clicking on the trash can icon.
To get the follow me icon get the like button code through your Twitter account. Then copy paste this code into your tumblr blog. Go to Tumblr Dashboard >> Your Blog >> Customize >> Edit HTML Here paste the Twitter like button and place it properly.
Go to your settings, click on "profile" and then "delete this image".
Follow the related link for instructions on doing this.
You can delete a tweet by hovering over it and then clicking on the trashcan icon.