The design at the rear of the ship looks pretty cool, lots of potential. You might want to add in a few extra bits and details around the ship to give the hull a more '3-dimensional' look (especially the front portion). People either tend to go a bit overboard with the small stuff, or not enough, and more often than not simply rows upon rows of ribbed portions are used (that gets old really fast). Just some raised plates or 'piping/cabling' can easily make a build look better and more detailed. Vents and recessed portions can also look really nice.
Along with physical accents, varying hull types can be used to add a textured feel to the hull. Based on the images you posted, it looks like you've built all of your ship with basic hull. Standard armor typically makes a better base to work off of (at least from an aesthetic standpoint) but basic has a lot of practical uses (mainly being lightweight, and easy to produce if one is playing with survival mode).
Systems can be whatever you want them to be. Smaller ships have more potential for mobility rather than offensive capability, but if you want to make a clunky, damage-dealing beast of a smaller ship, go right ahead.
All that aside, you've got a nice build in progress right here. Hope all goes well, and keep at it!
