Now, Coohom supports uploading your own scene during rendering action.
How to Upload Your Own Scene to Environment?
The new function is in Render > Environment > Uploads > Upload the scene.
Please note that the limit of uploading is 10 scenes.
1. Supported file formats: PNG, JPG.
2. Each image should not exceed 20MB.
3. The best recommendation for a image pixel is between 8000x4000px to 16000x8000px.
Additional custom background could be downloaded from here https://polyhaven.com/hdris/outdoor and make sure those images meet the upload requirements as mentioned above.