You can know more about your flash version used by Iceweasel on this page: http://www.adobe.com/software/flash/about/
Freshplayerplugin is now in the jessie-backports repositories and those who are more recent. You just need to install the package browser-plugin-freshplayer-pepperflash to enjoy it.
apt install browser-plugin-freshplayer-pepperflash
Some libraries needed are missing in Wheezy, this method will work only work for Jessie.
First, remove all the other flash plug-in to avoid conflict, then install the flash plug-in for Chromium : here.
Compiling Freshplayerplugin for Jessie
Make sure that you have access to the sources repository in order to start the compilation : see here
Install the required dependences for the compilation:
apt-get install cmake gcc g++ git pkg-config ragel libasound2-dev libssl-dev libglib2.0-dev libconfig-dev libpango1.0-dev libgl1-mesa-dev libevent-dev libgtk2.0-dev libxrandr-dev libxrender-dev libxcursor-dev libv4l-dev libgles2-mesa-dev libavcodec-dev libva-dev libvdpau-dev libdrm-dev libpulse-dev
As the project is still under development, this list can change. That can evolve with the needs.
Download and compile the source code in order to obtain the file: libfreshwrapper-pepperflash.so.
cd git clone https://github.com/i-rinat/freshplayerplugin.git cd freshplayerplugin mkdir build cd build cmake .. make
Deploy the library
cp libfreshwrapper-pepperflash.so /usr/lib/mozilla/plugins/
Restart Iceweasel for taking the change into account, and check that is working with the test here : http://www.adobe.com/software/flash/about/
Update the flash plugin
In our case, the library libfreshwrapper-pepperflash.so make a link with the plug-inpepperflashplugin-nonfree. You just need to update the Chromium plug-in to enjoy the latest version of flash from Iceweasel: see here.
Depending on the development of the project Freshplayerplugin you can, optionally, update libfreshwrapper-pepperflash.so by restarting the compilation above.