Not so long ago (Nov 04), I was in exactly the same position as you - coming from an RWS background and looking at a deck without scenes on the minors for the first time...It was daunting!
There are lots of threads in the Marseille section on reading the minors. Some are Marseille-specific, and some are more generally adaptable to all cards with non-scenic Minor Arcana.
A few pointers:
- first of all, go with the feel, the look of the card itself, its abstract design. It's like any abstract art, you can interpret its flowing lines, broken lines, shapes, etc.
- you can use a number of other methods on top of that, for more structure. A popular one is the number-suit method. Pick a system that suits you (classic numerology, 10 Sephirot, analogy with the Majors, etc.) for the numbers, then interpret that with the suit meaning (swords = mind, etc.) So for example, in classic numerology, 4 is stability, structure, and swords is mind: the card then can mean giving structure to your thoughts, needing to organise them (or it can mean - being too square in your thinking - just like RWS, there are different meanings).
- use the colour symbolism - again, I encourage you to experiment and research a system that suits you (or go with your gut as to what "red" means in such and such a place). A red sword is not the same as a blue sword. Emotionally, we respond to colours, and Vetrate is very colourful.
- shape symbolism is another useful method - I use it with the Tarocchi di Vetro, which uses geometric shapes consciously in its Minor Arcana. Again, there is much to be discovered on the meaning of shapes.
- Since you are dealing with stained glass windows, there have been much studies done about the symbolism of those. A rose is never just a rose in traditional stained glass art. Have a browse around.
- above all else I encourage you to develop your intuition. Because you are not limited by a scene, once you get used to working with non-scenic Minor Arcana you will find your imagination and intuition really take off in all sorts of directions.
Here is a very useful site to start
with your symbolism of numbers and shapes. Happy discovery!