Software needed:

Photoshop 5, FoT 1.27, Red!viewer latest version

O.k. This one is for new tiles. For simply altering existing tiles, see my other tutorial.

Firstly draw a tile, or take one from a scan or photo. You will have to select it then, I suggest using the Marquee rectangular tool, selecting a small area, then from Select->Similar, and if needed Grow (remember in Photoshop you can always go back if you make a mistake). In case this is not enough (you have to be as precise as possible) additionally use the magic wand and lasso tools until you have selected the entire object (also the marquee is handy if you zoom enough to select individual pixels). Just make sure you're holding down Shift while using these precision tools.

When you think you can't do better with selection, chose: Edit->Copy, then File->New->Paste (accept the program suggestions regarding sizes). This will create a new file with a Transparent Background, and your tile picture on top. It's somewhat easier to use it now, plus you want to have a transparent background, else it will show ugly later(along with the tile). There is another way to do this, just after selecting your picture select inverse and cut, but I wanted to be sure, so I didn't do anything exactly calm minded...

Now using the already described method, reselect the image/inverse it back (Btw, it should be in RGB color so if it's not change it). Now an important part. You have to know some rough proportionate dimensions of the tile (i.e. how big it should show in game) in order for it to work. I was making a table clock tile and these things have to be pretty small. So I checked the basic tile size(its roughly 76x40) and I made my tile at least 3 times smaller. I got lucky resizing it only two times until I had the desired effect. I suggest you resort to a similar method.

Not sure about this yet, but it doesn't hurt to Ctrl-C (copy) it. From the channels screen go and press the rectangular button next to the bin that says: create new channel. A black screen with the familiar selection ants will appear. Go to Edit->Fill->Foreground color (provided it is white, or else pick white manually)and 100%. Press o.k.

Now you will see that the area is white but some pixels may vary. That's fine. Leave it as is. Then go to the top Channel(RGB) and click the empty area next to it. If I'm not mistaken, the alpha should now display your tile. Save a copy as png (and preserve alpha channels), giving it a name you can identify easily, e.g. the tile's role in game. I named it clock1(as I recall at least).

Fire up the editor, tick convert directory from png to zar. You'll have to remember where you've put it. Close the editor and Start the latest RedViewer version. Open the zar you just made push the "Clip" button and add it there. Then select from the menu New->Tile, bring back the clipboard and export the zar (after selecting it-making it blue) to it.

Update: I noticed lately, some of my new tiles weren't looking exactly the way they should in game. It seems I forgot to mention the bounding box stuff. So after making your new tile go to Rendering->Bounding box (tick it if not ticked). You normally don't see anything. That's because you don't have a bounding box in new tiles. We'll have to make one. Just go to the bounding box area and type some dimensions in the three boxes that should display 0 (these numbers better be under 10). When you find the appropriate dimensions, go and push the edit-picture button (normally edit-none). You can now move the tile with the cursor inside the bounding box. You can change the dimensions appropriately if they don't fit (don't expect an exact fit).

Now all you have to do is save it under a different name somewhere you can spot it, I suggest the Test subfolder of tiles, or a new subfolder with your name. In this case you might have to put your name last in the form of F:\bos\tiles\Yourname in the relevant text file in the tiles folder. You've made your first tile and you're ready to use it!

Go in File->New->Tile, then click on the "export" button, the tile should appear in the viewer again. Enable the bounding box preview in the Render option, click the "Edit offset - Picture" then click on the picture to recenter it. You canused the a-s-d-w keys to adjust it better moving it by 1 pixel at a time. Also adjust the bounding box appropriately in the proper editboxes while at it then save it.