Image into a messagebox

is it possible to add an image like these
message-box-icons-md
into a message box? How?

best regards
Max

It depends on where you want the image to be. A messagebox is a container with some text and buttons, so you can add other objects to the messagebox but then you need fiddle around with the container layout.
eg if you want the image to be top center then it is easy

lv_obj_t * mbox = lv_mbox_create(lv_scr_act(), NULL);
lv_msgbox_set_text(msgbox, "Ask something?");
lv_obj_set_width(msgbox, 300);
lv_obj_align(msgbox, NULL, LV_ALIGN_CENTER, 0, 0);
lv_obj_t * img = lv_img_create(msgbox, NULL);
lv_img_set_src(img, ...);
lv_obj_move_background(img);

If you want the image to be somewhere else then you’re at the mercy of the container layout options.

Also consider using a font character as the image, if you won’t mind it being a single color rather than an image.