Plus (since 1996) They were uploaded to Chomikuj.pl as early as 2009, but the most of reuploads are from 2011 and 2014. The second Polish GSM operator (the first was Centertel), owned by Polkomtel (from POLska [Poland] + KOMunikacja [communication] + TELefonia [telephony]), which gained its concession for phone numbers in the 601-XXX-XXX range on February 1st, 1996. The commercial launch was on October 1st of the same year. Generally speaking, Plus was first in the many aspects. In 1997, as the first operator in Poland, they started offering SMS. In 1998 they launched the first prepaid phone cards as a service called Simplus (from SIM card + Plus). Additionally, their main competitor, Era, launched the same thing just two days later. In 1999 they signed a partnership with Nokia for the first 2G network in Poland, and in 2004, they were the first operator with 3G. The Simplus marketing campaign had one of the most recognizable and well-known ads in Poland, thanks to using the characters from the Italian animated series La Linea and its quirky humour. My second phone with a touchscreen, the Nokia C5-03 with a green shell, was from the Plus prepaid offer. I remember that the most impressive aspect of this phone for me... was the ability to remove the stock wallpapers, because it wasn't possible on my first phone with a touchscreen - the LG KP501 Cookie.

The oldest found set of 128x160px wallpapers, described as part of a custom set for the Sony Ericsson K800i from 2006. By "custom" they meant it was provided by the GSM operator, not the phone manufacturer itself. It consists of a static wallpaper, a probably screensaver, and a probably startup screen, but unfortunately I'm not sure if I'm correct about these two animated ones.

The standard set of the provider's wallpapers from around the late 2000s to early 2010s, which includes startup, shutdown, and screensaver screens, plus a static wallpaper. The first four are in 176x220px resolution, the second four are in 240x320px. On these ones you can see Plus' slogan, used from 2006 to 2011: Razem lepiej (Better together). Later they changed it to Wybierz swoje wszystko (Choose your everything).

Another set that was described as "custom," this time for the Sony Ericsson Zylo (or W20i) from 2010, which again consists of startup, shutdown, and screensaver screens, all in 240x320px resolution. If this set had a static wallpaper, then I didn't come across it.

At the end, there's a collection of three "scrapes" that were found in a random folders on the Chomikuj without any further information. A 101x80px static GIF that I'm not sure if was even used as a wallpaper. A 176x220px screensaver that seems to be a variant of the screensavers presented above, with faster and smoother animation. A version that is a mix of the standard blue and silver ones, but unfortunately I found only the screensaver screen (240x320px).