The add-layer type has many layer types available. From the description it is not always clear how exactly that layer would look like on a map.

e.g. a heatmap, a choropleth layer, a cluster-layer, a document layer,... all have very "characteristic" look&feel when they are added on a map.

It would be nice to show a little icon in the wizard (either as a replacement for the source-type icon, or in a tooltip) that shows to the user how that layer would look like. e.g. the heatmap-card could show the heatmap-color blobs, the choropleth-layer could show some thematically colored cartoon map, ...

CartoDB has similar UX.

cc @kmartastic @miukimiu @jsanz