Well, firstly, our terms, which are clearly shown on the first screen of the TCM, don't allow you to edit any of the cards the TCM has generated – so I'd ask that you not do so (and please take down and don't use any you have edited). If you're capable of creating your own sprites, I'd ask that you instead create your own trainer card in a graphics package if you wish to use your own assets – all the resources available to do so are freely available outside of Pokécharms, and it's not a difficult thing to do for anyone with spriting ability. For clarity, we do not allow you to screencap, download, or otherwise use the assets on the TCM in any capacity, so you'd need to source your own background, Pokémon panels, badges, and so on.
As for your question: we don't have any options similar to what you're asking for, and at this time we do not have any intention of adding that sort of feature. Any assets on the TCM are accessible to anyone using the TCM (and for no other purpose), and it goes against the purpose of the TCM – to be a simple solution for those who want to quickly make a trainer card, for those who may not want to create their own or lack the ability.
If you're already going to the effort of creating your own sprites, then you should be creating your own cards to use them on.