placeholder-img

/{}x{}
/{}x{}?bg={hex}
int—
int—
bghexcccccc

400x300
/400x300
400x300 blue
/400x300?bg=1e3a5f
600x200 orange
/600x200?bg=f97316
300x300 green
/300x300?bg=22c55e
800x200 dark
/800x200?bg=111827
250x400 yellow
/250x400?bg=fde68a

<img src="/400x300" alt="hero">
<img src="/800x450?bg=1e3a5f" alt="banner">

.hero { background-image: url("/1200x400?bg=1e3a5f"); }