I have put a couple of scanned flowers in some of my kits here
I got some lovely big fake fabric gerberas for $1 each at the local bargain centre and scanned them
here is how I scanned them (I think I originally got this tip on the computer-scrapping group on yahoo, but no idea who sent it - sorry)
arrange the flower head on the scanner bed (make sure the glass is really clean, no lint either) - now put a shoe-box lid over the flower, and then drape a dark piece of cloth (doubled if possible) over the shoebox lid so that all of the scanner bed is covered - this will prevent horrible shadows from extra light getting in. Now scan at at least 300ppi, save as a tiff file, then you can open it in your program and manually extract it from the background to make it transparent (fiddly and time-consuming process LOL)