. . . . who owns the concept(s), it's a good understood general rule that you toss some credit to the originator or even others who may have inspired you. You don't necessarily need to name names, just do like I've done in the past and mention those that inspired you (in a general format like this: "I'd like to thank everyone who has done this custom and inspired me to do my own" or something similar--you can also mention if it is a certain person who inspired you, such as Ptitvite, F_R, me, Joe Blow, Jane Doe, etc). It's just common courtesy--I don't think the kitbashing police will come after you if you don't, but it's just nice to do (same with writing and plagiarism--you cite a source when you use something in your work).