Blendfile with 4 good backpacks.

Are they game-ready?

hmhm depends.

-First: (of all) this is a blendfile because i don't want to export every format. So you have to export the files. I'll give u very good cookie:
https://github.com/mrtripie/Blender-Super-Batch-Export
Although you don't really need this for 4 objects.

-Second: textures need some work. Just baked them ++ subtle distorted the images a bit with gimp. Nothing out of the world, but with a couple of filters you can get your desired mid-low-res texture. hmmmm smtn else? OH OH SEEMS LIKE I LEFT TEXTURES WITH TRANSPARENCY. 

-Third: Before doing all this things, have you even scaled the objects properly? Or are you gonna do it on the way? hmm?

-Fourth: Enjoy the creation.