What I don't care for, however is the practice of cutting and pasting the same parts over and over again in to come up with new classes. Take Galaxy for example: We don't need the basic galaxy AND another class where the nacelles are one above and one below the saucer. AND we don't need another class where the nacelles are mounted off pylons that eminate from the saucer itself. AND we do not need yet another class where the nacelles are side-by-side over the rear of the saucer. To me this is redundant. There is no point in making half-a-dozen classes of ships with the same components. Neither would it be economical. That's just the first level of my beef.
Cut-and-paste is popular with fan art ships. Having built literally thousands of ships, many being fan-art, I can say that some folks, including those who wrote and drew the old FASA recognition manuals, just do not get it right. Many fan-art ships look good on paper, but cannot be rendered in 3-D. I remember trying to build a galaxy variant that showed in elevation the nacelles just above the center plane of the main saucer, with the bussard collectors starting somewhat forward of the hanger door area. The nacelles did not rise higher than the curve of the saucer. However, the bow view showed the nacelles just visible above the curve of the saucer. Worse, in plan, it showed the nacelles close together, flanking the hanger. If you went by the plan, the nacelles would have to be much higher than shown in the elevation, and even higher than shown in the bow view. If you went by the elevation height of the nacelles, and the plan view distance between them, then the first third of the length of the nacelles would be buried inside the saucer. Etc.
Worse though, is the practice of swapping around components from unrelated ships. Here is an example:
No offense to the artist... but that is just not right. What would be the point? And don't even get me started on swapping components from different technology generations. OK... they did it in "Best of Both Worlds". Does that mean it is canon? Not to me. How do I explain it? I don't.
Rant over. Now I will say this... there are folks out there who DO do it right. I am in awe at some of the model builders out there who can make wonderful new ships out of existing components. These gents have a way of making their ships look like they have purpose! One of the best has a huge array of starships eminating from a black shelving system. Each and every one of these are marvelous in their ingenuity... way beyond dihedral changes on pylons.