I have a base-64 image string:

R0lGODlhawAsALMAALu3ns/Kuv//9+zexPv33eovKfF8bfWzngAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACwAAAAAawAsAAAE/hCESau9OOvNu/+AJIxkaZ5oqq5s67ZBGAxvbd94Pg6xNBC6oHDoIvBkP4JyyWw6n9CodEqtRo8+q3bL7XqV2Nl3LC0wC0myN5xWuw0Fg9Ls/rLr+IJZj1/3xH1qfHyBW3eFW3p6B2YDhIhVh5BUfIx8jnSTU5KaUYRwBQcEj51QnKVnomaMo3uZqE6nsEZyBKy2rrNPsrAHBr+NP3ujbbq8qL6 KyqOjogRwzrDHpb6tiratRoq10n/FunFNSYOhocbeuku/lsrtrtHdSOlLq3qgoHxy36XTnXSizmoNgjernyZXoJplCzfP4KR35LIxa9gDwD5UdPQ5yzUxHRaL8fPmmGuy5weckB8vYnS3ByBD jxVVrlxmwKQemZNShjTljhvMECD7DBg61MoveopwatLZpyelV1J8Lo0ZaBG9os/UgUly4EcSrHNqKqk2VioZpnlIsbOXdKEydgbWtoIzAA60OmjrtPNaKV/EhEezMRJ1shkhgnaoNj2sjQ6hvyMbm7Hr1prZxECVJiKFqbFnvwLRgLaGRuTLs4rTvurMGrKcu6PtNbGEN7XeR3Ev6c51t7Bfwgx vkRqT9427VsIakcvtWNkA2qTl1s68s7oVnUSyaydixNv27+BvhAlPvvyKikDTq1/Pvr379/Djy58PNAIAOw==
This can be converted to an image by using Convert.FromBase64String() to get a byte array, putting the byte array into a MemoryStream, and creating a new Bitmap() by passing the MemoryStream object into its constructor.

What if, for whatever paranormal reasons, the last 4 characters are chopped off the string and I end up with this:

R0lGODlhawAsALMAALu3ns/Kuv//9+zexPv33eovKfF8bfWzngAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACwAAAAAawAsAAAE/hCESau9OOvNu/+AJIxkaZ5oqq5s67ZBGAxvbd94Pg6xNBC6oHDoIvBkP4JyyWw6n9CodEqtRo8+q3bL7XqV2Nl3LC0wC0myN5xWuw0Fg9Ls/rLr+IJZj1/3xH1qfHyBW3eFW3p6B2YDhIhVh5BUfIx8jnSTU5KaUYRwBQcEj51QnKVnomaMo3uZqE6nsEZyBKy2rrNPsrAHBr+NP3ujbbq8qL6 KyqOjogRwzrDHpb6tiratRoq10n/FunFNSYOhocbeuku/lsrtrtHdSOlLq3qgoHxy36XTnXSizmoNgjernyZXoJplCzfP4KR35LIxa9gDwD5UdPQ5yzUxHRaL8fPmmGuy5weckB8vYnS3ByBD jxVVrlxmwKQemZNShjTljhvMECD7DBg61MoveopwatLZpyelV1J8Lo0ZaBG9os/UgUly4EcSrHNqKqk2VioZpnlIsbOXdKEydgbWtoIzAA60OmjrtPNaKV/EhEezMRJ1shkhgnaoNj2sjQ6hvyMbm7Hr1prZxECVJiKFqbFnvwLRgLaGRuTLs4rTvurMGrKcu6PtNbGEN7XeR3Ev6c51t7Bfwgx vkRqT9427VsIakcvtWNkA2qTl1s68s7oVnUSyaydixNv27+BvhAlPvvyKikDTq1/Pvr379/Djy58PNAIA
When I try to use this, I cannot create a bitmap object. Instead, I keep getting "Invalid parameter used" when creating the bitmap object.

I can show you code if you'd like, but I have a feeling it isn't really a coding issue.