You can add rounded corners to a column background or border or a photo using the Radius setting in the Borders section of rows, columns, and some modules that let you set borders, such as the Photo module.
Tip: You can add other effects to photos, such as cropping them into a circle, in the Photo or Callout module. Click the Crop list on the General tab of the Photo module or the Image tab of the Callout module and choose a cropping option.