DeePsea supports the use of additional graphics (walls, floor, sprites, etc) not present in the main game IWAD file. Any graphics in a file opened are automatically recognized if they follow the game conventions. Graphics in separate files are automatically included by opening them. They do have to follow the standard conventions noted below, but nothing else is required.
There are a few technical details to learn. The wall graphic textures are created indirectly through the means of 2 other entries in the IWAD (or PWAD file. There is an entry called TEXTURE1 (and in some TEXTURE2) that contains the names of the textures you see displayed in the editor. These names are made up of a one or more smaller images called patches. The entry called PNAMES contains a list of the patches required to make up a texture. This method was used at that time since disk space was still expensive and in this manner they could reduce the size of IWAD file. The patch names can be seen by using the detailed graphics browser in DeePsea.
If you override existing patches with new entries (using the same lump/patch name), this will change any texture that uses that patch. The patch name is NOT the texture name, an easy mistake made in the beginning. Some people make up new texture names. To do this they created a new TEXTUREx and a matching new PNAMES entry. These names override the default game entries. DeePsea can also create new TEXTURE and PNAMES entries using the Texture Edit option in the F7 or Edit menu.
If these entries exist in a file separate from the level (or map), you may get confused when you read in a new level and the textures appear different than what you saw yesterday. Thatís because when you start DeePsea all the files are automatically loaded (option F5 menu). So even though you switched to a new map, the texture overrides are still present. To get rid of all the files, use the Close Files command under the File menu to start fresh. Either select the files you donít want or close them all and start over.
If patches are missing, blank texture panels are displayed. DeePsea doesnít care, but the game will not like this.