The test pattern was originally meant to help verifying connections in DIY boards (easy to detect&locate disconnected color bus traces with it) but it has some other uses too. However, it uses standards timings which do not necessarily match what you get with real linedoubled sources. The same would apply for fixed 720p etc. patterns so I’m not sure how useful they would be. A dedicated firmware with pre-defined and fully customizable patterns could be considered since that would not consume remaining FPGA resources available on ossc firmware.