Correct(?) assets are in the "bin/miecraft" folder.
Also remember to use all lowercase (for compatibility with Linux/Unix/etc.).
So if your modid is "nukes" stuff goes into "bin/miecraft/assets/nukes" (f.e. textures for block with setTextureName("nukes:nuke") go into "bin/miecraft/assets/nukes/textures/blocks/nuke.png").