An AJAX image preloader will definitely give a professional look to your applications. Here are 2 online tools that can be used to generate the gif loaders:
Ajaxload is an awesome tool that can be used to generate AJAX Loader Icons. To create one, you just need to select the indicator type, its background and foreground. Also, you can specify if you want to use a transparent color.
Preloaders.net is an excellent tool useful to generate GIF loaders from different categories: 3 dimensional (3D), Rectangular, Circular, Horizontal.
– the background and foreground color can be specified. A transparent background can be used too.
– you can specify custom sizes of the preloader
– an animation speed of the preloader can be set
Good luck!