To me, The top one is dark overall.
2nd one (well I guess it's not dark) the depth of field is a little shallow. Notice the final is out of focus while the section is in-focus. If you did this on purpose, OK, but if you'd like to get the whole thing in focus, you'll probably need to trade the monopod for a tripod so you can up the aperture to around f16-f20 (which will get more DOF) but the shutter will be so slow you won't be able to hold it while the photo is taken.
3rd one is more of a challenge because the chrome is about right yet the wood is way to dark to see the grain an details. You need some kind of additional light in the front to highlight the wood more, but will have to be careful a bout so you don't get too much reflection off the metal. These usually take some playing around to get somewhat right, but keep at it.
Each experience that's not a complete success is a learning experience...