Neomesh Image Converter can convert between most of the common image formats used on the Internet today. Convert between BMP EMF GIF ICO J2K JPG JPEG JP2 JPC PCX PNG PGM PNM PPM TGA TIF TIFF RAS WBMP and WMF.

The Resize feature allows you can create thumbnails. Its also good for making the images to the desired size before joining/animating them together.

Joining allows you to place all of your images into one image. Its great for making mosaics or placing textures. You can create animated GIF's using animation feature. Arrange the images into the desired order, set the time between the images and the number of times the animation is to loop, and presto you have an animated GIF ready for the web.