Hi everybody!
I'm using KDE 4.8.4 on Archlinux, and the layout based task switcher with large icons.
However, not all of the icons are really "large". In fact, applications from KDE or GNOME have large icons, and even Firefox does. The icons they use are apparently from the hicolor set. But some applications, such as Chromium and Vlc, which do have a large icon in the hicolor set, have a smaller icon in the task switcher.
Other apps are Skype, Pidgin, Pkgbrowser, Libreoffice.

I'm still looking for a solution through direct analysis, but in the meanwhile, does anybody have any clue on why it happens, and how I can fix it?
Thank you very much!

Check your icon theme. Some icon themes have icons for specific task in one resolution for example 128x128 but don't have for smaller resolutions like 64x64 or vice versa.
Icon folder
/home/user/.kde/share/icons/

Do you have the same problems with other icon themes?

The other reason may be how icons are scaled on this "the layout based task switcher". I don't understand what "the layout based task switcher" means for you. Could you provide screenshot?

Sure, here is a screenshot:
http://olorian.altervista.org/_altervista_ht/_jebliksbillede1-taskswitcher.jpg

I don't have any .kde/share/icons folder, nor in .kde4/ for what it might matter, and use the default oxygen theme.
I've tried changing the theme, but it only affected some applications. To be precise, after having switched back to oxygen, Dolphin decided to use Faenza's icon, which is also as large as it is supposed to be, while chromium hasn't changed its icon at all with any of the switches. [silly trouble which was solved by removing the icon kcache and restarting KDE]
The point is that chromium&Co. aren't affected at all, even if I successfully changed their default icons, their tasks still use the small ones.

Just have a look at the structure of your icon theme. For example oxygen
/usr/share/icons/oxygen
have many folders like 8x8, 16x16 and so on. Inside them are other folders like apps, mimetypes, etc.
Make sure that there are suitable icons for different sizes. You can re-size icon in gimp and add it to appropriate folder.
Icons are stored also in
/home/user/.kde/share/icons/
Try mixing icons from different themes adding to appropriate folders in icon folder structure. Before changes takes place you will need to change icon theme in settings to other and then chose the one you customized.

This is one possibility. The other is that there might be some issues with how this task switcher handles icons. So, write to the author of it about your problems.

It's weird. From here I got that such layouts are stored as QML files in that folder, and so I analyzed the relevant file, but I couldn't find any hint on where icons are taken from. On the opposite, I found out that the needed size is indeed 128x128, but I had already put such icons in .../icons/oxygen/128x128/apps/ without any result.
I think I'll try contacting the developer, thank you


---


How, I got a really fast answer. The issue isn't related to KDE, as the icons are provided by each application, so there's nothing that can be done about it.
Easily, I'd add. As soon as I have some more time to spend on it, I'll try making up a custom layout which uses only icons from the icon set you specify.