I agree.
As Johnner said above, 24-bit images obviously don't have a problem since each array element has all three 8-bit RGB values. However, I will add my opinion that there isn't quite a work around. If you take a look at the colors table of the incoming image for, say, an 8-bit image, there are indeed 256 elements in the color table. But the color table is customized to the image--for example an 8-bit grayscale image which returns a color array of 256 steps from black to white--and not the same color table recieved from the 'Get Image' invoke node (which is constant no matter what the image is inside).
So past the problem of the Picture2Pixmap.vi not returning a colors array, I'm thinking that even if it did, it would simply be the default color table that 'Get Image' returns. 'Get Image' isn't tailoring the 256 colors it outputs to the image like a normal image processing program (photoshop et al), reducing the colors down to the 256 closest colors represented. In 8-bit mode, the default color array only returns 11 gray values. Obviously that's not going to work for a grayscale image where 256 values are desired.
If you get a picture and save it as 24-bit, 8-bit color, 8-bit grayscale, 4-bit color, 4-bit grayscale, and 1-bit images, I've included a little test vi that will show the problem (hopefully) very clearly. Just open an 8-bit image, set the depth to 8 on the vi, and you'll see the test bitmap it saves is all funky since there's no color table included in the 'image data out' and the image in the 'Picture out' control has significantly fewer colors (picture out interprets the data with the default color table) in it than the 'Picture in' even though both images written to them were 8-bit to start with.
So...summary: Looking past the missing color table problem, unless a more typical graphics processing algorithm is included (to match the closest 2^1;4;8 colors) in reducing a picture control's default 24-bit information to 8, 4, and 1 bit information, even if they fix Picture2Pixmap.vi to return the color table the 'Get Image' invoke node returns, it's still not going to preserve a non 24-bit image.