What feeling or aesthetic do you want your ships to evoke? Are they kind of industrial and grimy like OT rebel ships? Clinical and stark like OT Imperial ships? Elegant like the Naboo/Nubian ships to better fit a more elegant time? Or sort of weirdly organic or insectile like the CIS droids?
Do you use starships from the actual PT? Perhaps EU ships that you feel fit the aesthetic you’re aiming for? Invent your own de-evolved forms of ships from the OT or just wholesale make up new designs in your head?
Personally I use the basic image designs for some of the EU ships that I think feel Star Warsy (such as the Z-95 Headhunter or the CloakShape Fighter) but then just completely retitle them and repurpose them for roles needed in the movie outlines.