Thumbscrew
Thumbscrew is a cute practical image utility that should be part of any Macintosh user application library. The application allows users to quickly create thumbnail size images by simply dragging and dropping the images on a window.
The Thumbscrew 1.0 manual says it best...
Screw it! Making thumbnails for the Web used to be painstakingly slow if you wanted to apply borders, drop shadows, transformations, alpha channels, and so on. Or if it was fast, you ended up with a boring field of rigid columns and rows. Thumbscrew allows you to quickly and easily chew through a bunch of images, applying scaling, random rotation, border, and drop shadow to each - even resizing the original, and processing the batch as a whole afterwards.
The application preferences were pretty easy to understand. I really like how when you do a bunch of images and have a "Max. Angle" set, it will randomly select an angle size.
The problem is that the application is longer maintained and appears to have gone to vaperware. The application was created by Zachery Bir in 2004. Contact him at his website or on Twitter.
You can still download the application at various internet sites, including MacUpdate. The application works perfectly fine in El Capitan (Mac OS 10.11.2) and it's free so it's worth trying out if you need to quickly create thumbnails from a set of images.
Picturesque
A good alternative to this application is Picturesque. It has a few more bells and whistles that Thumbscrew had, but doesn't have the Max Angle effect. I personally liked version 1 of Picturesque since that had the ability to create thumbnail images of PDF documents.
Picturesque has the ability to set Perspective, Reflection, Shadow, Corners, Stroke on each image. You can save your configuration so you can use them again and again. Picturesque cost $14.99 can be download from the App Store. You can download a demo version on Acqualica website.