Asciimilator is a free application which lets you convert any bitmap to cool looking html files that use ASCII characters to represent the bitmap pixels.
It uses a combination of black and white color to give the over all contrast of the original picture being converted.
You can configure various factors like the following
Pixel skip x: skip every "x" vertical pixel if you want to
Pixel skip y: skip every "x" horizontal pixel if you want to
Pixel offset: start with "x" Pixel
Clipboard: copy image data from clipboard
Font size: HTML character font size can be changed
Background: control the background color
Black / White: is used in combination with the "Auto Pixel" feature, activate this checkbox for darker backgrounds- deactivate for lighter backgrounds.
Auto Pixel: It will automatically determine what pixel is used by examining the color intensity
Pixel Text: Enter a text (disable "Auto Pixel" to use this feature) , it will be looped and used as characters in the output image.
Color Code Compression: Larger images can get quite big, so you can use this feature to reduce the output file size.
This could be the best free software which helps you create ascii images from your bmp images.