I have an InstallShield project done using InstallShield 2015 LE for Visual Studio 2013. I customized the 2 images (banner and welcome). They are appearing correctly on Windows Server 2012 and Windows 7, but they don't appear at all on Windows Server 2008 R2.
Global Dialog Image: < VSSolutionFolder >\Internal\Setup-Welcome.png Global Dialog Banner: < VSSolutionFolder >\Internal\Setup-Banner.png
These images are displayed by Windows Installer. It's possible that the Windows Server 2008 R2 variant lacks support for png files, or that something else about these particular images is throwing it off. I would suggest trying (at least as a test) converting your images to jpg, or possibly finding a different image tool to recompress them as pngs. See if those work.