I think this is fixed on 0.9.1, try updating and let us know if it still happens.
Image Class and Custom Class
Image Class and Custom Class - what it affects?
'ADMIN CONTROL PANEL > MANAGE > CATEGORIES'
- If you set a background image, the image class can be used to change how it is stretched. See this article for options
- Custom class is exactly what it says, it allows you to define a class that is applied to the category. In Lavender, this is used to position blocks in certain arragements (e.g. 3 to a row, 4 to a row, etc). In Persona, they are not used, but you can still used them if you wish to apply special styling to certain category rows.