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)
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.
Save a gif to your computer and upload it as your profile picture on Twitter.
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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.
Follow the related link for instructions on doing this.
Go to your settings, click on "profile" and then "delete this image".
You can delete a tweet by hovering over it and then clicking on the trashcan icon.