Link buttons are used to direct users to other websites or files for futher information.

Attachments can be either documents, pictures or other file formats.  Each attachment is saved to a SharePoint document library. 

Signatures are collected and stored in a SharePoint document library. 

Blank Spaces can be useful for spreading out fields on your form.

You can add images from your devices camera to a form.  This is particularly useful while completing the form on a mobile phone. 

A header can be useful to break up sections within your form.