File Juicer
File Juicer for macOS
Overview of Formats

Search & Extract

Images

jpg jpeg 2000 gif png pdf wmf emf tiff eps pict bmp

Video

mov mpeg avi wmv

Sound

mp3 wav System 7 au aiff

Text

ascii rtf html

From:

avi cab cache chm dmg doc emlx exe ithmb m4p mht mp3 pdf pps ppt raw swf wps xls zip and other formats

nib - Interface Builder files

Nib Files
Interface Builder is one of the applications which come when you install Apples developer tools (XCode).
Nib files does usually not contain images. They are separately stored in the resource directory. They contain the layout of of the user interface of applications.

To inspect many nib files you can download XCode from Apple, or find it on one of the CD's which came with your Mac.
You need to sign op to Apples free online developer program first: Apple Developer Connection