First all you need to decide on what type of theme that you will use a concept, many creators will try and copy the classic rider waite system of 78 cards.
Tarot can be based on anything as long has its got the 22 major arcana and 56 minor and court cards.
What did you have in mind?
Many people think anything with a full picture on the card face is a Tarot Deck.
By purist definition a Tarot Deck is not an Oracle Deck and an Oracle Deck is not a Tarot deck. A Tarot Deck has 22 Major Arcana cards that follow a set pattern of #0 is the Fool through #21 The World, and the Minor Arcana of 4 suits of 14 cards each, numbered 1-10 plus 4 Court cards, totaling 56. If you are not following this pattern it is not a Tarot deck no matter what your theme is, and calling it a Tarot deck if it isn't will confuse and confound people who want to buy a Tarot deck.
An Oracle deck can be anything - any number of cards on any theme with any images you choose - as long as you provide an explanation of what each card is supposed to mean and how the cards are meant to be used. If you look at a Lenormand Deck you will see that it looks nothing like a Tarot deck ... because it isn't! :)
And what i find most annoying is people who think just creating a non substantial 30 card deck that doesn't even resemble a real Tarot deck? ''But then insists on calling it a Tarot deck???? why
Yes, but the problem will be that if you do not follow a 'traditional' Tarot deck layout then you will find that the Tarotists will not buy it, other than maybe those that collect decks for decks' sake. You have to produce something the projected audience will buy. Merely calling it 'Tarot' will perk the Tarotist's ears up - but when they find it bears no resemblence to a Tarot deck - for whatever reason - they are not going to buy it.
Actually that Sordid Lives deck is not a good example of what you're talking about. It's actually a "Majors Only" deck with maybe a few extra cards mixed in with the usual 22. Tarotbear gave a favorable view of it.
I mostly agree with Tarotbear's definition but should add that the Fool is not always numbered "zero"