14.1, 14.2, 14.3 - https://www.progress.com/documentation/sitefinity-cms/custom-dam-provider-and-thumbnails

CustomDamProviderConfiguration.cs

using System.Collections.Generic; 
using System.Collections.Specialized; 
using System.Linq; 
using Telerik.Sitefinity.Configuration; 
using Telerik.Sitefinity.Modules.Libraries.BlobStorage; 
using Telerik.Sitefinity.Modules.Libraries.Configuration; 

namespace SitefinityWebApp.CustomDamProvider 
{ 
    public class CustomDamProviderConfiguration : IBlobStorageConfiguration 
    { 
        /// <inheritdoc />  
        public IEnumerable<DataProviderSettings> GetProviderConfigElements(ConfigElement parent) 
        { 
            return Enumerable.Empty<DataProviderSettings>(); 
        } 

        /// <inheritdoc />  
        public IEnumerable<BlobStorageTypeConfigElement> GetProviderTypeConfigElements(ConfigElement parent) 
        { 
            var providerTypes = new List<BlobStorageTypeConfigElement>(); 
            providerTypes.Add(new BlobStorageTypeConfigElement(parent) 
            { 
                Name = "CustomDamBlobStorageTypeName", 
                ProviderType = typeof(CustomDamProvider), 
                Title = "CustomDamBlobStorageTypeTitle", 
                Parameters = new NameValueCollection() 
                { 
                    { DamBlobStorageProviderBase.ScriptUrlKey, string.Empty }, 
                    { DamBlobStorageProviderBase.SupportedThumbnailFormatsKey, ".jpg, .jpeg, .png, .gif, .webp" }, 
                    { CustomDamProvider.UrlKey, string.Empty }, 
                    { CustomDamProvider.ClientIdKey, "#sf_Secret" } 
                } 
            }); 
            return providerTypes; 
        } 
    } 
}