The following icons are from either the Crystal icon set, http://www.everaldo.com/crystal/, or the Oxygen icon set, http://www.oxygen-icons.org/ . These icons are licensed under the LGPL, available here: http://www.gnu.org/copyleft/lesser.html

As such, use of these icons is covered by the LGPL license, and not the regular Paint.NET license.

Crystal
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Icons.DentsEffectIcon
Icons.EllipseToolIcon
Icons.InkSketchEffectIcon
Icons.InvertColorsEffect

Oxygen
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Icons.ColorPickerToolIcon
Icons.CurvesEffect
Icons.EdgeDetectEffect
Icons.LineToolIcon
Icons.MenuEditCutIcon
Icons.MenuUtilitiesSettingsIcon.24
Icons.MenuWindowToolsIcon
Icons.OutlineEffectIcon
Icons.PaintBrushToolIcon
Icons.Settings.Tools.24
Icons.TextToolIcon