Using custom field to show personalized product?

I want to sell personalized products and would like to have a thumbnails of the outcome shown during checkout. I would like to know what options I have to accomplish my goal.

Some background info:
- the whole shopping process will not require a user login or registration
- a different application will create the productthumbnail (i.e. a black T-shirt with picture on it)
- that application should add the product to the cart (just black T-shirt)
- when the customer goes to checkout the product should be shown using the custom thumbnail
- when the customer buys 3 of the same T-shirts with a different picture, 3 T-shirts should be shown seperately, each with its own thumbnail

I thought that having the design application create a (variant) product for each personalized T-shirt will kill my setup eventually (to many products of which they will all sell just once). So I guess I have to think about something with the "Custom fields" maybe?

Does anybody have some interesting ideas on this?

I've seen this before on a different website, to give you an idea:

Thanks,

is it also possible to have several of the same products with different customfields show up as separate products?

Product1, Customfield: myfirstproduct, qty. 1, price $1
Product1, Customfield: mysecondproduct, qty. 1, price $1

Could it be an option to create a variant of a certain product on the fly using php code?

When the customer approves his T-shirt design php would then automatically create a variant of a specific product, add the corresponding preview thumb with it. Then afterwards use cron to cleanup created variants for each product. Or would this create to much loose ends in the database or otherwise influence the performance or neatness?

But will that create a new item-line in the cart for each same product ID and each with there different design (in your example referenced by a different custom field content)?

Because earlier you said it is not possible if the product is the same.


T-shirt type A, Photo1/customfield, amount 1, price $10
T-shirt type A, Photo2/customfield, amount 1, price $10

Just tried it on the demo site, seems to work. Now I have to think what the best way is to use the custom field for processing and attaching the designfile to the product without showing the custom field in the cart.

What would be the best way to fill the custom field when adding the product with a direct link? The custom field will not be filled by the customer in the webshop, but has to be filled by my customizing application.

I could have the Flash design application add the product using a link or something, but then I would need to know how to include the customfield data to push with the productitem
Or I can use PHP code to add the product to the cart. But somehow I would need fill the customfield with a designnumber or ID which I can use for the further processing and printing of the T-shirts.