Create blanks using the sizes you listed in photoshop, set all the SDTV artwork to DV NTSC aspect ratio *before* you begin. Create all your artwork for those sizes. Use Save For Web to save the artwork in as high visual quality as possible with as small a file size as possible. You may find that you have to save some as .jpg and some as Png24 or PNG8 to achieve the best look for the smallest file size. Assuming the developer knows what they are doing, they will be able to handle whatever filetype you use (png8, png24,gif, jpg are the supported types). Ideally, the completed channel including the artwork should be < 500k when it is zipped.
- Joel