only thing I can come up with for getting unexpected row sizes is if you are trying to use a dbc file from another version or expansion of the game on a version it didn't come from. if thats the case, there is your problem.
what are you using to edit your dbc files? secondly you're not really clear in what you're referring to replacing.... are you making new textures with something like photoshop? or are you just trying to re-assign stuff?
if no one answers you, it's most likely because no one has a clue and because your post was pretty vague, there's not much to go on either.
I will try to be more clear, and give an example:
There is a pink succubus display ID, say, 666. And there is another display ID of the same pink skin and model, though different scale size for example, 999. I know how to import and replace a skin, and by doing so both 666 and 999 would get their textures replaced with my own (edited through GIMP or PS). I'd like to replace the texture for only -one- of these, not all. 666 would be the original succubus skin, while 999 would be my own, edited version. Sorry if this is still confusing, I tried to explain it the best as I can.
The CreatureDisplayInfo.dbc should be MoP, I'm pretty sure, but I will look into it later.
I use MWS to extract and make the MPQs. I am told it is very outdated, though I am unable to work properly with Ladik's MPQ Editor for some reason, whereas MWS works fine for me when doing simple things like replacing textures. Also, I used MyDBCEditor to try and edit the CreatureDisplayInfo.dbc to include my custom texture path on one of the display IDs.
Didn't mean to look as if I was impatient, sorry for that.