To rename a gallery as uploader: Open e-hentai.org, go to My Uploads, click on "Manage" next to the gallery you want to edit, then change the title, check the checkbox below and click on "Save Changes". Done!
If this is not possible anymore (happens if the gallery is too old), then you can start rename petitions. Open a gallery and click on "Petition to Rename" on the top right. If enough users vote for a rename petition, the gallery will be renamed.