How to customize indicators icons?

Hi, I found a icon theme really beatifull, but indicators applet and weather applet uses horrible icons, guess it is missing so uses the mate default icons, now I wonder, How can I customize those icons and put others more beautifull? what name should it have and where should I move it? or there is application that can change it graphically? Thanks for helping.
PD: I tried to change the icon for a game putting my personal image in /usr/share/icons/hicolor/apps (where the original icon is from) and selecting it, but when I select the image it dont recognize it and use the launch app default icon, but when select the same image in my personal folder (/home/my-user/...) it change the icon with no problems, anyone knows why?

Are you using .png files? That is the file extension you need. I use my own Desktop icons for many programs and don't have any problems with them being recognized. I also just leave them in user/share/icons. Easier to find that way. I would say also make sure you are using a small enough picture for the icon.

If you are trying .ico files I don't think they will work, I think that .ico is for windows, but am not certain on that. Here is one that should work:
Risk of Thunders

Download a .png or jpeg (convert to a png) file from the Internet. Now open a terminal to open caja as root and save your .png file at usr>shar>icons>mate>48x48>app.(I don't usually go all the way to apps, but I save mine at icons)
Then go to System> Look and Feel> Mate Menu. Pick your program, (say Mate calculator) and click on properties. When the launch properties box comes up click on the square in the upper left corner with the icon, or missing icon symbol that will open where the icon is saved usr>shar>icons>mate>48x48>apps. Navigate to your icon and click on your icon that will make it the default icon for the system.

I used svg and png files, all in square size, the problem was that if I put the image in /usr/share/icons/ it don't recognize the file, but if is in /home/user/
It's the exact file but in different folder

Try checking if the permissions are the same.

But do u know where indicators applet icons are? and what icons should I change?

The weather icons are at usr/share/icons/gnome/22x22/status
I don't know how you change it on the indicator applet.
usr/lib/mate-applets or usr/lib/mate-indicator-applets seems like there is some kind of file that sets them.
What I gave you works for desktop or a panel icon.