FastStone Photo Resizer is a very easy to use free software for batch conversion of your images. This batch image converter can do batch conversion of images, and also batch rename them. The interface is intuitive, and easy to use, and the conversion speed is pretty fast.
FastStone Photo Resizer can do a batch conversion of images to following formats:
JPEG, BMP, GIF, PNG, TIFF and JPEG2000
While doing batch renaming of images, FastStone Photo Resizer can rename them in sequential order. To add images for batch conversion, you can select images in bulk from your drive, or do a drag and drop using mouse.
Apart from doing batch conversion of images, FastStone Photo Resizer also provides basic editing capabilities for images. You can Resize, crop, change color depth, apply color effects, add text, watermark and border effects. For more advanced editing features, you can try Paint.Net, or Picasa.
FastStone Photo Resizer is really good at batch conversion and renaming images, and the best part is that it is totally free. Download links and Video Tutorial at the end.