FastRes 

FastRes lets you quickly change your screen's resolution and color depth, from the system tray. It is small, and takes up very little memory.
quickres resolution tray

Blaze ImgConvert 

Advanced batch image conversion supporting over 140 formats and an entire arsenal of options and features. Comprehensive support for compression, sub-formats, color depths, naming templates, and resizing/rotating in the same operation are available.
convert conversion resize rotate image graphics colorspace multi-page rename afp ani awd bmp