So weirdly enough the flowers on Rose's shirt appear to be the Stewartia pseudocamellia (notable here is the clear camellia-like profile) which is in fact a flower called shara[沙羅] in Japanese, like the name of his zanpakutou, Kinshara[金沙羅]: "Gold Shala." But from what I had always gathered the zanpakutou had a lot of clear references to a different species of slower entirely, the Shorea robusta also shara[沙羅] aka the sal/sāla/shala tree.
So to start, in Buddhism the sal tree of scripture is arguably more mythical than real, and so it's associated with the former in Japan, but natively in India it's associated with the latter, which would seem to account for the confusion, except that the actual design of Kinshara clearly evokes the long whip-like vine shape of the Indian Shala rather than the Japanese pseudo-camellia, which just grows on normal tree branches.
I kinda wonder if Kubo didn't just google it and grab whatever looked good without any regard for them being the same/different flower(s) or not.
Kensei's shirt seems like a pretty straight forward reference to his name Muguruma[六車] meaning "6 Car/Vehicle," something Kubo used to base his bosozoku gimmick off of in TBtP, so the 6 bars just look like stylized bikes or cars in a sort of motorcade.
It is also, perhaps coincidentally... the daoist bagua trigram ☷ for kun[坤]: "Earth" (as in the opposite of "heaven" but it's elemental association is actually [地]: "earth" but in the dirt and soil sense) But incidentally the Earth trigram is associated with the epithet Liù duàn[六斷]: "Six Fragments/Sever(ed things)" and the traditional chinese character duàn[斷] simplifies to [断] which is the same kanji in tachikaze[断地風]: "Sever (the) Earth Wind." The Six is there, The Earth is there, the Sever is there...
Again I'm not even sure this was intentional but it does happen to link the name Muguruma[六車] to ☷ and [地] to Liù duàn[六斷] the sword Tachikaze[断地風] even if it took a seemingly improbable game of 6 degrees from such an innocuous design, of just 6 lines, to get there.
