Java SE (Java Platform, Standard Edition)

I've been working on a peer-to-peer project lately and I wanna create a user-friendly interface.
Basically I'm trying to find a set of nice looking icons much like those in, say, Microsoft .NET Webmatrix or SharpDevelop. I used to utilize the icon set of the Eclipse Platform, but it's not that "modern" anyway.

I certainly don't wanna create those icons myself for I'm hardly competent when it comes to art. So my problem is where do I find such an icon set?(It should be in formats like .gif or .png so I can easily use them in my Java project). Thanks in advance.