From Miranda IM - Wiki
Customising icons is one of the ways to change the look and feel of the user interface.
- Browse the icons category on the File listing
- Extract the archive into Icons folder
- Navigate to Options->Customize->Icons
- Select the set of icons you want to change from the list on the left.
- There are two ways to load icons, in whole sets or individually
- Sets: Click Load Icon set... and select the icon file.
- Individually: Click Import icons >> ("Show expert options" must be enabled)
- Open the icon file in "Icon Index" window.
- Drag the icons you want to change on top of the old ones.
- Most .dll files in the Plugins folder contain (the default) icons.