Code:
// Obtain the image data
byte* yourImageBytes = obtainYourImageBytesOverNetwork();
// Add the image data to the engine's buffer.
add_buffer("mybitmap.jpg",yourImageBytes,countOfYourImageBytes);
// Now you can load from this buffer
BMAP* bmapToDisplay = bmap_create("mybitmap.jpg");
// Don't forget to release the buffer
add_buffer("mybitmap.jpg",NULL,countOfYourImageBytes);

I haven't tested or compiled the above code. It's just meant to give you the basic idea.

Always learn from history, to be sure you make the same mistakes again...