Please recommend pretty Java Swing components library

Why not use the standard java Look and Feels there are plenty:

• JGoodies
• JTatoo
• Jide look and feel
• Liquidlnf
• Napkin LaF
• PgsLookAndFeel
• Quaqua (looks like aqua from MacOS X)
• Seaglass
• The Alloy Look and Feel
• The native for your system
• The nimbus LaF
• The substance project (forked into the Insubstantial project)
• WebLookAndFeel

Also see here for more free L&Fs:

• javootoo.com
• Synthetica Themes - Custom L&Fs

Alternatively you may want to know how to create your own:

• How to Write a Custom Look and Feel

Or Modifying the Look and Feel might be what you need

Java Look And Feel Libraries/Engines:

• Cezanne L&F engine

References :

• Best Java Swing Look and Feel Themes | Top 10
• oracle.com - Modifying the Look and Feel
• wikipedia.org - Pluggable look and feel
• Java2s.com - Look and feel
• Java Look and Feel (L&F)

I would recommend javaFX, it supports CSS. Sky's the limit plus you get a friendly UI builder by oracle check them out here!