Well you can thanks to an app called OblyTile.
OblyTile is a tiny little application that runs out of the box (no install process, just needs administrative privileges) that lets you create custom app tiles for all of your applications from image files.
When you launch OblyTile (which can be downloaded from here), you are greeted with a Modern UI styled box shaped app which has 4 key features:
1) App Name
2) File path of the applications main executable file
3) File path of the square shaped image you want to use as the tile
4) Create the app tile
In the tile name, you want to type the name of the application, but if is too long simplify the name such as just “Word” instead of “Microsoft Office Word 2003” (yea I love old school office). You can hide the text if you want so it doesn’t show on the tile.
Then for the program path you will want to trace down the location of the app. so for an example if it is Microsoft Word, then you will want to go to “C:\Program Files (x86)\Microsoft Office\OFFICE11” if you have the 64bit version of Windows or “C:\Program Files\Microsoft Office\OFFICE11” if you have the 32bit version of Windows and then find the word exe.
Then click the magnifying glass (search) icon in the middle of the two buttons to preview the tile and if it looks ok then click “create tile” and it will automatically be on the start screen for you which you can position where ever you like on the start screen.Keep doing this for each app you have directly on the start screen and hey-presto there is no tile that looks out of place so it looks a lot better and is more eye catching.
Once again you can download the app from here.