Unfortunately you’re not missing it. The icons are not customizable and are determined by the device handler used. There’s a lot of people not thrilled with the new app (and im putting it mildly)
But what you might lose in looks you can make up a lot in function. For example, I have that same remotec relay on my fireplace. Custom code allows access to the advanced settings of the device, including being able to set an auto off timer. I can now use double tap on my ge switches too. These things were not possible in wink. I use this one for the remotec if you’re interested
https://github.com/ragross/SmartThingsPublic/blob/d95cf59e6b2bd2fd2075beb19109856f1033c336/devicetypes/mikemaxwell/remoteczfm80.src/remoteczfm80.groovy
If you really don’t like the app, there are 3rd party alternatives, like Sharptools, that can control Smartthings through their own interface. The 3rd party alternatives were discussed here , but some charge a fee depending on what features you want Third party app to control SmartThings hub?