The kind of picture you are talking about is that the account user has set up a signature file.

Baidu Post Bar sets the signature file, and it takes 3 months for registered users to set the signature file in Post Bar.

Here's how to set the signature file:

1. Select the picture you want as the signature file and upload it to your Baidu Space Album. (Because the picture link only refers to the pictures in the post bar and space).

2. Click "Post Bar" on Baidu homepage, and there is a "Settings" option next to "Personal Information" on the right. Click the "Settings" option.

3. After completing step 2, you will enter the "Basic Information" page, and next to the "Basic Information" option is "Signature File Settings".

4. Click "Add a set of signature files", enter the name of your signature file (fill in casually, this name is used to select signature files when you have multiple signature files), then paste the link of the picture you uploaded to Baidu Album in the "Picture Link" text box, and finally click "Save" to finish the setting.

When you post a reply in the post bar, please check the "Use signature file" option, select the name of the signature file you want to use, and then click the "Publish" button.

I hope I can help you.