Not sure what you are searching for... Ideas to make (one of) these dioramas, feedback, or suggestions on different equally epic duels?Firstly I suppose feedback on whether they would be good in principle, then ideas on composition and numbers of models etc.
Some of the best dioramas have the perfect number of models. But it's hard to figure all that stuff out when I've never attempted a proper diorama before.
Also where to place the main focus, distance between them and heights etc. Does the eye 'follow a path' through something like this, or just go for impact?
Ah, got you. Well feedback-wise I reckon that yours are very good ideas! Besides, after having seen what you can do with Green Stuff, if somebody can sculpt Sigmar that one is you.
I wouldn't go for Horus vs. the Emperor because... Well, it's a tough nut to crack. EVERYONE in the hobby has heard at least once about it, and everyone has a different mental image of it. This means that you either do this well, VERY well, or you risk to make the viewer turn his head before he even starts to look at details.
HE vs DE has been done countless times before, people looking at the Diorama would exchange Caledor vs Malekith for High Elf Hero X vs Dreadlord Y (Malekith wasn't wearing his usual gear here because he hadn't fried yet... Right?).
Sigmar vs Nagash sounds very intriguing! First and foremost, Nagash is supposedly one of the most powerful beings in the Warhammer world, yet GW doesn't talk often about him. Sigmar instead is well known, yet nobody ever tried to represent him. Finally, both carachters can be easily recognized by everyone.
If my memory serves me well the duel happened in the newly born Empire. Why don't you try Inquisitor scale? That would look epic! I wouldn't put too many casualties on the base, as you want the main characters to be the focal point... But If you do put them than make sure they are all members of Sigmar's Umberogen Guard!
Also, I don't think that developing a story is the way to go. These guys are the ultimate heroes (or fellons) of their respective races. THEY have to be the focus, and the scene should look dramatic, powerful, with the two figures intertwined in what is their age's greatest duel, a muscled barbarian rotating on himself, muscles tensed, veins bursting, hairs flying (or whatever hairs do), hammer glowing with power, gritting teeth, pure fury on his face, furry loincloth & boots, ermine mantle. Nagash instead... Well, he is basically a robed skeleton, but I imagine him to be Sigmar's opposite. Where the first is fury incarned, the second is calm and concentrated. Where the first is throwing himseld at his opponent the other is thinking at how to best him. Maybe he's formulating a spell, sword in mid air to parry Sigmar's furious slash, his staff glowing before casting a spell.
And that's it!