Twitter is the popular online social network that lets you post brief status updates. Each time you post a new tweet, it shows up in the reading lists of the accounts that follow you on Twitter. A small thumbnail of your Twitter avatar displays next to each of your status updates, and a slightly larger thumbnail appears on your Twitter profile next to your bio. Users can see the full-sized version of the image by clicking the thumbnail on your profile. If you'd like to edit your Twitter profile's thumbnail, you must first change your Twitter image.
Log into your Twitter account and click your username in the upper left corner. A drop-down menu appears.
Click "Settings" in the drop-down menu.
Click the "Profile" tab on the subsequent page.
Click the "Change Image" button next to the thumbnail of your current Twitter avatar. A form appears below the field.
Click the "Browse" button to browse your computer's hard drive for your new image. Double-click the image file's name on your hard drive to select it for uploading.
Click the blue "Save" button at the bottom to save your new image to your Twitter profile.
Be patient if you don't see the changes immediately live on your profile. Twitter may take a few minutes to update your profile with your new image, and may take up to an hour to edit the thumbnail that appears on users' timelines.
Twitter images must be no larger than 700 KB in file size, and must be only in .JPG, .GIF or .PNG formats. Twitter displays thumbnails as squares. If your image is rectangular, Twitter displays it in a cropped form, and part of your image may be missing from your thumbnail. To avoid this, upload a Twitter image that is as wide as it is long. Twitter displays the full image in your thumbnail.