My pages don't end in any extension, is this ok?

I don't know.

Try

 http://httpd.apache.org/docs/2.0/misc/rewriteguide.html 

Code (markup):

Also this might help:

 http://www.addedbytes.com/cheat-sheets/download/mod_rewrite-cheat-sheet-v1.png 

Code (markup):

 

http://httpd.apache.org/docs/2.0/misc/rewriteguide.html

Code (markup):

Wow!
It was really complicated for Just rewriting one rule!

Can I ask anybody's help ??

 

Try this.. (The very last line is my addition)
The "index.php" coming in the links must be suppressed by specifying it in the pattern.

Options +FollowSymLinks
RewriteEngine On
#    leave just a normal / (slash) if the script is installed at root level otherwise enter it's folder here ex: /wscript (! no trailing slash)
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond $1 !^(index\.php|install|scripts|fonts|uploads|robots\.txt|sitemap\.xml|favicon\.ico)

#    if wscript is installed in a subfolder, add it before index.php ex: RewriteRule ^(.*)$ /wscript/index.php?/$1 [L] otherwise leave it as is
RewriteRule ^(.*)$ /index.php?/$1 [L]
RewriteRule ^wallpapers/show/([0-9]+)\.html$ index.php?/wallpapers/show/$1 [L]

PHP: