Breakdown of Mira, los vasos han quedado pisoteados.
mirar
to look
el vaso
the glass
haber
to have (auxiliary)
quedar
to be left, to end up (in a state)
Questions & Answers about Mira, los vasos han quedado pisoteados.
Why use han quedado instead of están or han sido?
Using quedar + past participle emphasizes the final result or outcome of an event. While están pisoteados just describes their current state (they are trampled) and han sido pisoteados focuses on the passive action (they were trampled by someone), han quedado pisoteados highlights the permanent or surprising way the cups ended up after the event occurred.
Could I use the pronominal se han quedado here instead?
You could, but the non-pronominal quedar is much more common and natural when talking about inanimate objects that have undergone a physical change, damage, or destruction. Quedarse + past participle is usually preferred when talking about people and their emotional or physical reactions, such as se ha quedado sorprendido (he was left surprised).
Why is there a mix of participles here, with quedado ending in -o and pisoteados ending in -os?
They serve entirely different grammatical roles. Quedado is part of the present perfect tense (han quedado), and participles attached directly to the auxiliary verb haber never change their ending. Pisoteados, however, is the resultative participle functioning as an adjective describing the subject (los vasos), so it must agree in gender and number (masculine plural).
What is the difference between pisados and pisoteados?