Upload iCloud photos with OS X 10.7 My only Mac is so old that it only runs a maximum of OS X 10.7 which does not support iCloud Photo Library. 

I want to upload a few thousand photos from my hard drive to iCloud Photo Library one time and that's all. 

Is there a way to do this with my old Mac?
You should be able to do this at icloud.com. After you sign in, click photos, then upload at the top. You should then be able to select the photos you want to upload and click choose. Note all the photos must be individually selected: you may not select a folder.
You may alternatively drag them to the photos interface on icloud.com.

Obviously, it will take awhile for a few thousand to upload.