Finding the right synonym for "vain pretension" can be crucial when trying to convey a particular tone in a piece of writing. Some synonyms that may be useful include "ostentation," which refers to a showy or excessive display of wealth or knowledge, and "arrogance," which connotes exaggerated self-importance. "Pretentiousness" may also be a suitable alternative; this term specifically refers to someone who tries to come off as more cultured or sophisticated than they really are. "Conceit" suggests excessive pride or self-regard, while "vanity" implies a focus on one's appearance or the superficial aspects of one's life. Ultimately, the right synonym will depend on the context and desired effect of the writing.