I have Nop Commerce version 3.60 and I wanted to install this plugin. I was using it before with version 3.5 and there was "already designed" ribbon images in different colors blue red green that you could just upload.
Maybe there is some kind of error that prevends the ribbon images from showing and prevends you from uploading your own images. Can you check your System -> Log for errors related to Product Ribbons ?
Error Value cannot be null. Parameter name: picture
Error Value cannot be null. Parameter name: picture 7/6/2015 6:32:07 AM View Error A public action method 'RetrieveProductRibbons' was not found on controller 'SevenSpikes.Nop.Plugins.ProductRibbons.Controllers.ProductRibbonsController'.
System.ArgumentNullException: Value cannot be null. Parameter name: picture at Nop.Services.Media.PictureService.LoadPictureBinary(Picture picture, Boolean fromDb) at SevenSpikes.Nop.Plugins.ProductRibbons.Controllers.ProductRibbonsAdminController.a9Ir2tq6e(Int32 ) at SevenSpikes.Nop.Plugins.ProductRibbons.Controllers.ProductRibbonsAdminController.PrepareRibbonPictureModels() at SevenSpikes.Nop.Plugins.ProductRibbons.Controllers.ProductRibbonsAdminController.TuGEtQc4M() at SevenSpikes.Nop.Plugins.ProductRibbons.Controllers.ProductRibbonsAdminController.RibbonPicturesList(DataSourceRequest command) at lambda_method(Closure , ControllerBase , Object[] ) at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) at System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass33.<BeginInvokeActionMethodWithFilters>b__32(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult)