Module Class Suffix is a parameter in Joomla! modules. [...] Setting this parameter causes Joomla! to either add a new CSS class or modify the existing CSS class for the "div" element for this specific module -- Joomla Glossary

On the module variations page, several module classes are showcased. As you can see, multiple module classes can be added to a module to combine styles. If you want to use multiple suffices on one module, you have to separate the classes with spaces.

The module class suffix can be added in the 'Module parameter' (Module Manager > Your Module Name > Module Parameters > Module Class Suffix). Every style, label and icon can be mixed, leading up to 300 styles for your modules!

Available module classes suffices

Boxes

• box1
• box2
• box3
• box4
• no-fx

Labels

• label-hot
• label-cool
• label-new
• label-sexy

Icons

• icon1: Twitter
• icon2: User
• icon3: RSS
• icon4: Cart
• icon5: Lock
• icon6: Tag
• icon7: Home

Patterns

• pattern1: Stripes
• pattern2: Retro
• pattern3: Paper
• pattern4: Leather
• pattern5: Flowers
• pattern6: Dots
• pattern7: Cubes
• pattern8: Abstract