Just export the image as your choice of 2D file under the File/Export/2d Graphic - drop down option.
Go to File -> Export -> 3D Model. Export it as a COLLADA File (*.dae) file. Click on the Options button and make sure that Export Texture Maps is checked. Go to the exported file location. In the directory, there should be a folder with the exported file name containing all of the textures.
Importing .skp file to C4D automatically generates a folder with textures next to the .skp file
When .skp file is imported to 3ds Max, it stores texture files to ..\3dsMax\sceneassets\images. You can find textures there. You can also export fbx file with embed media option selected (in the export dialog window), so it automatically generates a folder of textures together with the fbx file.
Import .skp file to Rhinoceros 3D. Open material editor (Panels->Material editor). Select any material that has texture on. Click on the texture name (in the Textures section), click on the three dot button. You can now see all the textures, it should be in the ..\AppData\Local\Temp\embedded_files directory. Feel free to copy and paste the textures to any folder you like.