advice

the attatched images are not of your work, but rather similar to what you're wanting to create?

If so, you're going to want to start looking at sculpting programs and I highly recommend investing in at least a cheap bamboo tablet to get started and see if you like it. Sculpting is far different than traditional box modelling and can be quite taxing on your system, so make sure you're computer is also up to spec before investing too much time and effort into the learning process of it.

As for software, I personally use Zbrush and I absolutely love it, in 4r7 they introduced features to better acommodate box modelling as well! But its primary focus is still sculpting. By far, it's one of the best investments out there in terms of software. If the price tag is too much, I believe they also still offer sculprits for free, which has a lot of handy sculpting tools. I believe even blender has started to introduce sculpting, however I can't attest to how great they are and what you may be able to accomplish with them.

Best of luck, and feel free to contact me if you have any more questions or want some more guidance as to where to start! :)

This pic is my work with zbrush..i use a little bamboo tablet.. What we want is to improve and look for some documentation or manual to help me in this .
The pictures are all my creations

Hehe! Bamboo tablet rocks! Love the size! :) Honestly, for me personally, I looked up a LOT of videos while learning the more advanced features of zbrush, again youtube is your friend! If you're looking for more in-depth and instructor styled learning then I HIGHLY recommend you check out digital-tutors, that site has everything!

Best bet though is to find something in particular that you want to improve (say alpha texturing or something, maybe nano meshing) first place I ALWAYS start is youtube. From there if I don't feel comfortable enough yet to play around with the concepts, I'll hit up digital-tutors, and typically by then I'm in zbrush playing with the new techniques.