Real newb question

Just coming from the plastic and wood side of modeling, I am wondering about bashing models. My interest lay with ships models, so all the builds I've looked at so far has been in that section. My question is when building kits, and not models from scratch, are you pretty much locked into building as the designer intended or can you convert the subject somewhat? I'm not thinking about altering things with the aid of computer graphics prior to printing. I haven't noticed it so far and thought I may have just overlooked it. That was something I always enjoyed doing (as if building it as intended isn't enough of a challenge!!!).

Kurt