For simple web mapping, recently I have been experimenting with Leaflet and Esri-Leaflet quite a bit. For simple and quick mapping, Leaflet using Esri-Leaflet to support Esri published services is a very viable solution. One difficulty I initially struggled with is getting point symbology from a feature service to display when adding a feature layer. It took the better part of a week, fiddling and cursing with with it off and on, to figure this out. My pain is your gain, though. Here is the solution.
You can find the url of the image by going to the REST endpoint. the images will be displayed. Right click on the image and copy the url of the image. This will be the url to use for the icon. The other url, the url for the feature layer, is simply the url of the REST endpoint.
Although documented in pieces in other places, it took me a while to piece it all together. Hopefully you find this much earlier in your search for solutions and it makes your life a little easier.