Kostia, changes you would like to make can be done via CSS. Please note that avatars are used sidewide and if you change their size, this will result in a a lot of glitches everywhere they are used.
Default avatar size is 40X40. Let's change this to 70X70 by adding following css in admin panel>> appearance >>edit theme>>"Css" tab:
.ow_avatar {
height: 70px;
width: 70px;
}
.ow_canvas .ow_avatar img, .ow_canvas .ow_lp_avatars img, .ow_canvas .ow_newsfeed_avatar img {
height: 70px;
width: 70px;
}
Result:
As you can see avatars are big now. But:
1. You still have old 40X40 borders on the background of each avatar. To remove them you will need to create a new background image of 70X70 size or remove background border image completely within
.ow_avatar {} class via CSS.
2. All places where avatars are used ( for example "Newsfeed") are now not aligned properly. You will need to edit more CSS to get this corrected.
Unfortunately I can not provide you with the CSS code to correct every single item across the site. You will need to find a designer to complete this work for you or do this yourself.