Just_Jim wrote:Can they be .png images?
Yes. In fact, that's probably the best format to use because (G)Zdoom can read sprite offsets that are coded into the png files.
Just_Jim wrote:Do they go in a directory \sprites in the .pk3 Pack?
Yes, but see below.
Just_Jim wrote:What width x height will gzDoom support?
I don't know what the limit is, but it's likely to be bigger than you are going to need.
Just_Jim wrote:Does gzDoom need to be told to override the "wad" sprites?
GZdoom (and Doom generally) works on a last-loaded gets priority basis. So, if you load your pk3 after the WAD, your PK3 will override anything with the same name that has already loaded (with the exception of certain cumulative lumps).
However, I don't *think* that there is an easy way to replace sprites automatically scaling them. What you will have to do is write new DECORATE definitions for the actors and give them new scale factors. To be fair, some properly DECORATE coded enemies for Darkest Hour wouldn't go amiss anyway. From memory they are mainly just minimal changes from the Doom original actors using a bit of DEHACKED here and there. In fact, I think I may have had a hand in a little bit of that myself. It was a long time ago.
Another alternative, I think, would be to define all the sprites using a TEXTURES lump. You can define scaling and offset values there IIRC. However, I'm less familiar with this and someone else might need to chip-in to cover any problems that are specific to replacing sprites this way.
Oh, it's worth mentioning that this mod "forced" (or should that be "Forced"

) me to dig out my copy of Darkest Hour and Dawn again. I have to say, despite its age it really stands up well and still feels very fresh and well made. The only thing I felt was a bit aged was the enemies I mentioned. At the time I don't think that making enemies using DECORATE was even an option but I always felt that it was a shame that a lot of the bad guys were, fairly obviously, really mainly just re-skinned Doom enemies.