Why useless a TImage in the
GUI instead of a TBitmap directly?
But you know that you not only deactivate the theme, but also the new APIs of RichEdit, the TreeView, the Open and SaveDialogs, the TaskDialogs and who knows what else because you switch to the ancient versions of these DLLs?
Microsoft is also in the process of finally removing this old junk.
If it's about speed and resources, e.g. in VMs, Remote Desktop and Co., then deactivate menu and window animations, as well as transparencies and AeroPeek.