Some ideas:
* You can buy very fine metal chain that is around the same size on the epic models as the chunky plastic chain on the W40k models. It's a little harder to stick down but you can have it exactly where you want it.
* Spikes can be made of plastic or metal rod, possible sharpened to a point. You could probably drill a sequence of holes in the top of the tank, glue metal spikes in that are also going through a long thin rectangle of cut plasticard so they look a lot like the spikey bits on the W40k ones. You could even cut off, drill through and include heads from epic models on them, though then you're getting really fiddly.
* Bodies are tricker to do an get right, but should be doable. You'd have to select a model that could be converted to look dead, either by bending it if it's metal or by cutting and gluing if it's plastic.
*
Skaven throwing stars can make good spikey blades I find.
* Parts from chaos models in 40k and Warhammer occasionally have small scale chaos stars that could be carefully cut out and glue on. Otherwise perhaps a green-stuff press mould could be made of a star and used to apply a star where you wanted this? - Apocolocyntosis uses this technique whereas I haven't (yet) so he should be able advise if it's possible and give you tips.