Of course, if you have a professional graphics editing tool like Adobe Illustrator or Photoshop (and others), editing and creating such images will be a breeze. For the rest of us, who neither have the use or scope for such tools, there are a few options.
Paint, the default Image Edit that comes with Windows (mspaint.exe) is able to save an existing image in one of the below formats. The scaling feature is not very good and so you should use the image editor that comes with Microsoft Office, to get the size right.
A second, and probably better, option would be to use something like Paint.NET. This is a free tool which can be downloaded here.
The resolution and colour depth for the welcome image is as follows:
- 160 by 72 pixels and 256 colours for the DM460x
- 132 by 90 pixels and 256 colours for the DP480x
- 132 by 72 pixels monochrome for the DP460x
- 320 by 240 pixels and 16bit (R5-G6-B5) colour for the SL40x0
The file format is Bitmap (.BMP). Note that when the welcome image is used, the radio name text will not be displayed during the power up sequence.