The IC-705 has an option to store and show a selfmade picture during bootup. However there is two pitfalls you have to care about. Otherwise the picture cannot be read. I created my pictures on Linux with Gimp which is a very handy tool for such tasks.
The first thing to make sure is that the resulution of the picture is exactly 480x272 pixels which is a 16:9 format. Larger pictures or 4:3 pictures may have to be scaled and/or cropped to fit. This is relatively easy achived within Gimp.
The little more complicated part is to store the image in the correct format. Basically it is a bitmap file ending in .bmp with 24bit color depth. This is done in Gimp using the “Export as” dialog and selecting the 24bit option in the advanced options. A second requirement is to set the option not to write the color space information under compatibility options. See the following screenshot:
This picture can be copied to the folder
IC-705/OpeningPicture and then configured in the IC-705’s menu under SD-Card options. The result looks rather nice: