When you first register your Twitter account, you are assigned a default avatar. That is a PNG format image with an unhatched egg as you can see below:
So what does this image mean? Literally it is an unhatched egg. An immature bird. I assume nobody wants to give that impressions constantly 
Now… What does that “default avatar” mean in twitterverse. If you leave your avatar as the default (and NULL) possible meanings are:
- You do not take Twitter seriously
- You are just lazy
- You are a spammer
- You are nobody
- You are so unsocial that you cannot have a friend with a camera to take your photo
- You are unsocial and do not have a camera
- You are unsocial and do not know auto-shutter function of your camera
- You are a company / group that does not have a logo
- etc.
Best Practices for a Twitter Avatar
On Twitter (and in social networking) people would like to see yourself. Nobody likes to communicate and share things with stylistic images, cartoon characters or so.. Some ideas:
- Put your own photo that reveals your own face (preferably professionally taken) showing how a nice person you are…
- Use a plain background and a high quality picture. Do not let other details shadow your face…
- You may use a a full body or a bust portrait picture, but make sure that it shows “who” you are.
- You can also have a stylistic representation of yourself (if you are a designer or have a designer to draw one for you), you can use it as soon as it really represents you uniquely.
- Avoid webcam shots.. They are low quality and blurred.
So, what if you are not a single person. Some ideas below:
- For a couple, use a picture together
- For a brand/company/group/team, use the logo
- For a “robot”, use the picture of your “robot” 😉
- For a pet or plant, use a picture of it
