Thanks for the posts, everyone!
Feline fanatic, your description is very good, with the comment about doing the design on the top initially to give guidelines kind of what I was expecting. Thanks for the comment!
Jennifer23, I didn't really have anything in particular in mind, as another post here on QB sent me off checking out some specialty threads, which then led me to bobbin work, which then had me posting the question.
My DSM is a Viking, and I discovered there is a "specialty thread bobbin case" for my machine, so I'm definitely going to check that out.
In addition, awhile back, I had an opportunity to buy some extra bobbin cases for my longarm (which is also a Viking), so I will probably use one of those as my "bobbin-work" case, and mark it with a Sharpie or something if I can get the tension loose enough for it to work.
Now, another question somewhat related... and Jennifer23, your comment got me thinking of this as well....
Could a specialty thread be so thick/large/special that you cannot put it through the tension disc's? And how would you thread it then?