When a Space is exported into HTML, attachments with Chinese characters were disencoded. Therefore, the image couldn't be displayed in a page.
The steps are explained in the following:

1. Create a page consisting of Chinese characters
2. Upload image files (eg. 我哈.jpg) with Chinese characters
3. Display the image, !我哈.jpg!, within the page
4. Export the space to HTML
5. Unzip the file
6. Open up the page with Chinese characters (converted to pageid)

Clearly, the image is not displayed