Figured I make a thread about it, since I'm wanting to do this, but I had no luck with it yet...Anyways the goal here is to trick the DSi into thinking a pic from the PC has been taken with the camera so you can display/edit it on the system. If you have an idea on what to do or have tried something post it here, I would like to hear about it and I'm sure everyone else would too, lol.

ur really desperate to figure this out aren't u? lol just take a pic of the image while it's on ur computer monitor

It doesn't work, you just get whiteness...and it doesn't really turn out that good looking anyway...

do u have a flat-screen monitor? that's what i have and it works pretty well

Yeah I do...I can try it again...though last time I got a big white bright screen. Ugh, nevermind...its coming out clear now, lol. Ah well, guess this could work, still though if anyone finds a way to get it to read the actual pics let me know.

if it's too white try turning down the brightness of ur monitor or turn on a light in the room to make the camera adapt to the lighting

I'm guessing I didn't hold it to the monitor long enough since at first it lags and has the bright screen, though after a few seconds it clears up and dims down.

yea, that's the DSi changing its settings to obtain a good picture

most digital cameras and cell phone cameras do this

I'm used to the crappy cell phone camera then. XD
I don't play around with cameras much, lol.

lol well i do, i took photography classes last year in school

I tried taking a pic of my avatar at school and the pic looked like a quilt! Weird...

I guess it does start looking weird when you hold the camera up close to the screen...
Well, since it is my thread I'll ask an off-topic question here instead of making another thread for it. XD

When I try to check for updates for the DSi it says there's an update for the system, and when I hit update it then says its already up to date...ugh. What's going on here?

re: the original topic: editing the EXIF data alone doesn't work. i think there's something on the DSi itself that tells it how many images should be present and what specifically to look for on the SD card... if you attempt to delete all the images from the SD card after backing them up onto your computer, for example, when you replace the SD card into your DSI it has a bunch of placeholders with 'image file corrupted' or whatever instead of just looking clear.

steps I tried myself that did not work:
(a) physically edited my image to the 640x480 pixel size and saved it at photoshop's jpeg compression level 2 (to get it down to the kb-size range of all the other images i've pulled from the DSi so far)
(b) copied it to my DSi's SD card
(c) renamed the file I was replacing, then changed the name of my edited file to that file's former name
(d) used an EXIF data editor (Exifer, a pretty good freeware Windows-based program) to copy the data from the file i was replacing to the edited file
(e) deleted the file i was replacing (it was already backed up to disk anyway) and then popped the SD card back into my DSi

that alone did not work. I don't know if the DSi actually looks at when a file was actually created or modified instead of just the EXIF data, or if it's got some kind of internal table that knows exactly how big each file should be (since I couldn't get it exactly that size, only in the general range -- 70.something kb instead of the 77.1 kb the original file was). i also noticed that, after copying the EXIF data between images, the edited image's thumbnail changed to that of the original file.

anyway, at this point i got bored and just snapped some DSi pics of some stuff I wanted to use as my default top-screen image. it's just easier at the moment until someone figures it all out, lol.