What is the ruling on earning profit from designing T-shirts on foreign websites, what are the conditions for designing permissible T-shirts, and is it permissible to design a T-shirt whose content alludes to a foreign song?

The consideration in website designs is their freedom from prohibitions and Sharia-forbidden elements, such as full images of animate beings, or images of women, or that the design's content alludes to a forbidden song, as that would be an endorsement and promotion of it.