Well, this is indeed very helpful to me, especially for indexing. But, I am experiencing some trouble, in the way that when I attempt to import I am told the sprite is unindexed.
(EDIT: Do disregard everything below, I did some reading and porkiewpyne had the exact same problem as me, but he found the solution)
I believe I have correctly followed your Irfan tutorial, and I was able to lower the pallet to 16 and then rearrange the two necessary colours, resulting in a similar and somewhat broken image. It seems that when I paste the unindexed image over the indexed one in Paint (Windows 7) it also carries over properties such as... well, not being indexed. Actually I think I can test this theory...
Okay, I tried again. I lowered to 16 and went about that colour swapping business, and then I closed and reopened in Irfan. The box for 2 (black and white) is now ticked, as apposed to what I ticked (16). I can only assume this is normal behaviour.
Then, I pasted my unindexed sprite over it (in Paint), and checked again in Irfan - now the box for 256 is ticked. This seems to be my problem.
I imagine there is some thing I am doing wrong, something easily fixable to be quite honest XD I do have a habit of buggering up the simplest of things.
Some information that may also be of relevance and use is that I am trying to replace Lickitung with a Mew sprite that has been edited intentionally badly to be wearing a top hat, amongst other accessories (The hat is drawn in a colour that is actually used by the original sprite, I am definitely under 16 colours). In Ruby version. I dislike Lickitung. Intensely. Top hats are cool and so is Mew.
I understand that is a lot to read, and that most of it is unnecessary drivel. Thank you in advance.