The only guild I belong to is the Tulsa Modern Quilt Guild. There is a whole lot of study/thought about what makes a quilt "modern". There is an excellent national Modern Quilt Guild and they have a definition on their website:
Modern quilt characteristics are but not limited to: use of bold colors and prints, high contrast and graphic areas of solid color, improvisational piecing, minimalism, expansive negative space, and alternate grid work. Modern Traditionalism, or the updating of classic quilt design is aLso seen as modern quilting.
The annual QuiltCon show is a great show of spectacular modern quilting. There is a huge amount on the web, and most modern quilting guilds have websites for you to browse.