there are 30wt threads that may work for you- check the Superior Threads website to see the variety they have to offer....also Atlanta Thread company is another source. I generally turn to Superior Threads for options when i can not find what i need from Connecting Threads (or locally)
generally if i want a design to really stand out i make that happen with either Contrasting color- or a double batt (or wool batting) & dense quilting- i don't use a heavier thread.