This brilliant classic game tool looks very promising. It's plans are to be able to export/import the graphics, sounds, music, and other important files from all common classic DOS games. It even plans to be able to view the levels of the games. Right now it's in beta, but viewing and extracting graphics from Cosmo is almost completely bug-free, as are the routines for many of the other games. This is well worth your time downloading. You can also edit tiles of Cosmo and reimport. Editing the images and sprites are soon to come.
This is the first graphical level editor for Cosmo. It's a fully functional and pretty easy to use DOS editor, although it appears to have a bug with a sprite limit and not reading the bottom row of tiles in a level properly. It's still in a usable condition however, and it's definitely the best choice when it comes to editing Cosmo levels.
This was the first Cosmo editor to exist. It is hard to use as it has a text display and it describes itself as "a level editor that should really only be used as a level viewer." Visit the site for more details here.
This is a couple of utilites you can use to view the pictures from Cosmo. This download only includes the source (one file in C, two in BASIC). It has been superceded by Wombat Game Tools, however the source in this download may still be useful to those curious.