The use of thread or fiber as a symbol of fate dates back to Greek myth, with the three Moirai, or Fates, spinning, measuring and cutting the thread of life. In Homestuck this symbol translates to the use of fibers as symbolic of timelines.
The Felt, in addition to being named after a material composed of fibers compressed together, are repeatedly implied to be made of the stuff;
Rose Lalonde, the Seer of Light capable of reading the one most fortuitous timeline, is frequently seen carrying a ball of yarn; one long thread (she also uses it on to whack her Time player on the head on more than one occasion). The needles she uses to work her yarn are also the same kind used to work the Land of Heat and Clockwork’s Beat Mesa.
Perhaps at more of a stretch, the trolls’ time player Aradia is associated with rams and sheep, which are bred for their wool.
The phrase ‘fabric of spacetime’ is used a couple of times throughout MSPA - once in reference to English’s coat (which it stands to reason might be made from the same stuff as his leprechauns’ skin) and once in Problem Sleuth (in a sequence often connected to Kanaya, who decorates her hive “with FLORA and FABRIC, as delicately or aggressively as inspiration demands,” possibly symbolic of her role as a Space player) - showing the obvious connection between the Space and Time aspects, with fabric being composed of fibers woven together each way.