Within Teamwork Chat, users can attach any file type to a message simply by clicking the file attachment icon left of the message field or drag and drop the file into the message field:

Note: The maximum file size or upload at any one time is 2GB.

When posted to a chat room / conversation, the file type will appears along with the file size in kB:

When sending images within chat, it will show a preview of the image. Users can click on these for a larger view within Teamwork Chat.

For more information, see how you can use markdown to format messages