The Hippocampus is a modified Ringworks Wanderer; there's an illustration of one of the basic model on page 311 of the Core Rulebook. The Hippocampus probably looks pretty much close to that from the outside, so you can use that art to help you imagine the interior layout.
I can picture a take on it akin to a double-decker train car. A small four-seat bridge (with a design that makes it look like a cockpit from the outside, in turn making the whole ship look smaller than it actually is) to the fore. In the standard model Wanderer, I imagine the bridge opens into a compartment featuring an aisle flanked by passenger seating; in the case of the Hippocampus, those seats have been stripped out and replaced by bunks. Oh, and in either version, probably restroom(s) at the back, flanking a hatch to a cramped engineering compartment.
Between the bridge and the passenger area, I imagine a ladder, lift, or staircase leading down to a long cargo bay in the ship's belly. In the case of the Hippocampus, half of this baggage area has been replaced by life boats accessible from the passenger cabin. (Although when I ran this, I think I ran the numbers and decided escape pods were more affordable on the ship's BP budget.)