They both look good. I can see them working well. The harsher edges to the restraints now also have a more authoritative feel.
Ofc xmoon has the final say on numbers. I'm just stating my opinions

http://cgtextures.com/ have lots of great images that can be used. The rusty selection is limited but I'm sure there is a portion of one that you can trim down and use.
I found uvmapping a real headache. But after a while it clicked. Like any of the other parts, it just a case of giving it a go.

I'd highly recommend you to neither use the decimate modifier nor starting all over from scratch again. There are much simpler methods for reducing the polycount.
For example grab an edge loop (ALT+RMB), press STR+E and select 'edge slide'. Then slide the edge loop until it intersects with the edges next to it. Press W and click 'remove doubles'.
I like this better than the decimate modifier, since it gives you more control over the mesh's geometry. You can actually decide where to save polys.

That said, you could really use textures/materials for your models. As KotLPL said, Cgtextures is a nice source. However, I'd recommend you to give project/clone painting a shot if you have good reference pictures.
For a chrome-ish look, I tend to set a gray diffuse color and a white specular color. Turn the hardness up and activate mirroring. 0.4 is a good value for reflections. In the standard scene, you may not nptice the effect of the mirror, therefore I'd suggest placing an image of your desired scene behind your camera. Now it's just a matter of playing with some values in the material tab.

Hopefully this answers all your questions.

They're both good, but design number 1 just wins it imho.

@xpadmin are we able to realize/mod the handcuffs into game by the actual progress of wiki?

@tomahawk308

The double clamps can be used for it to some degree.
But it would be far better if we a special handcuff object for it.

This "handcuff" object would lock automatically when near the wrists.
So the character also has to have "wrist" position specified.

So it is very well possible, but not through modding alone.

nice you mean not the object from clamps? so creating a special object behavior class for handcuffs? but we can use this 3d model further or? creating object class would it be possible in future?

what i must do to realize this? copy the code from clamps into this 3d modell or? and what you mean wrist position and how?

xpadmin??

Yes the clamps have similar behavior as the handcuffs would need. However the handcuffs would need tracking towards hands.
So a new handcuff class would need to be added by us.

nice could you help to realize the handcuffs with clamps object class?

would the handcuff class be integrated in future 3.1 or 4.0?

If you or someone else can make a good looking (normal poly count ~2-4 k) handcuff, I will see what I can do.
Preferably a low and high poly version.