Unfortunately it sounds like you'll need Trading Paints Pro to see any of this on Custom made paints.
I'm guessing because iRacing implemented support in Sim it means I can create liveries and view spec maps locally however not see them when uploaded to Trading Paints.
This is correct, for anyone else who is wondering. This feature requires an additional "car_spec_xxxxxx.tga" file to be uploaded to Trading Paints, and Steve Luvender from Trading Paints was very blunt in his stance that server hosting isn't free, so they are placing this feature behind the "Trading Paints Pro" membership at an annual cost of $24.00 USD per year. This is consistent with their other "Pro" advantages; the additional "car_decal_xxxxxx.tga", as well as the ability to upload Day and Night paint schemes to one car at the same time.
You will still be able to see Spec Maps locally, if you add the "Car_Spec_xxxxxx.tga" yourself, or share it via another hosting service (TS File Browser, for example) and all hosted Trading Paints spec maps will be downloaded/visable to you whether you are "Pro" or not.
Another option to circumvent Trading Paints, while still getting Endurance skins out there, would be via the iRacing Forums. For each Endurance event, there is usually a way to submit paint schemes to the Broadcast crew, and I believe those files are made available to everyone on the service to download. Can you confirm that
@Noodleguitar ?
Anyways, here are some more examples iRacing showed off on the Twitter: