I'm sorry, I only half understood that last response.
The command I posted generates the name from the camera ID and the date/time the download started. So if a download_images command downloads more than one image from a camera, only each file will overwrite the previous one and you will only end up with one file.
So is there a way to make it work? I'm not fully following, sorry :-(
That depends what your requirements and workflow are.
If you did download_images after each shot, the names would be unique with the existing command. However, this is probably inconvenient.
If you replace ldate with mdate, the name will be generated based on the time the image was taken, according to the camera date. This will give you unique names (as long as images were taken more than 1 second apart, which is practically guaranteed on cheap cameras) but unless the clocks on your cameras are synchronized, images from the same shot on different cameras will have different names.
There are other other ways you could generate the name, listed in the help for the imdl command, but the only ones that are image specific from the camera file / directory (which I think you didn't want to use) and the date related ones.
An alternative would be to reset the camera image numbering before each session, and then using ${name} or ${imgnum}. The camera number tries to follow the highest number image on the card, so if you put a file called IMG_9999.JPG in the current image directory, the next one will be IMG_0001.JPG.
I will probably add a feature to multicam to insert sequential numbers, so you could say take 5 shots and download images number 1-5 for each camera, but I'm not sure when I will get to it.