Yes, exactly. Don't ever touch the bin folder, it is the src folder you should change.
You should have something like
mcp/src/Keep of Metal and Gold/assets/komag/...then textures/blocks for blocks, textures/items for items...
pack.mcmeta is completely optional.
I got it working! With a little foolery with Eclipse, and it turned out I needed /mcp/src/komag/assets/komag/textures. Bit redundant, but it works! Something with taking the "komag.assets.komag.textures" entries, turning them into source folders, then removing them from the build path kicked Eclipse and Minecraft in the rear and she's working like a charm, thankee!
For those looking here for a solution to this problem, the aforementioned folders are in the /mcp/src folder, ie the Minecraft project, and NOT your mod project folders.