Tetradraw

Tetradraw is a fully featured ANSI art editor for *nix operating systems (Unix/Linux). The editor was developed by John McCutchan and is available for free at Sourceforge. The built-in "MultiDraw" feature allows two users to edit the same file in collaboration over the Internet.
The editor is part of the Debian and other small Linux distributions.
Tetradraw list of features
* ANSI art is not limited to a certain amount of lines. Your art can be an unlimited length.
* Informative status bar.
* Built in ASCII character table.
* Built in Chat interface for MultiDraw.
* A powerful block command. Featuring character and colour replacement and fill. Flipping on the X and Y axes. Transparent Layer mode.
* 20 configurable character sets.
* A powerful interface.
* Supports the ANSI, ASCII and BIN file formats.
* Complete access to the source code to make any improvements or changes
* Many configurable options that can be changed from internal options screen.
* A separate ANSI viewer: Tetraview.
* Fully compatible with all DOS based ANSI editors and the Linux console.
* Auto backup of the image you are working on.
* Built in quick help screen.